CoChat
Sign Up
Cited by 3Dermatologic Treatments and ResearchSkin Protection and AgingFacial Rejuvenation and Surgery Techniques

A Randomized, Investigator‐Blinded, Split‐Face, Controlled Trial Assessing Efficacy and Satisfaction of CE Ferulic Serum Following Nonablative Fractional Fraxel Laser Treatment for Photoaging Skin in Chinese Population

Open access
Qin, Xiaolei, Zhai, Jinlong, Zhou, Chenxi, Wang, Yanmei, Chen, Mengjiao, Zhu, Lin, Shi, Qi, Chen, Weiliang +3 more·2025·Journal of Cosmetic Dermatology
DOI 10.1111/jocd.70251PMC PMC12104010
Open this paper in CoChat — free accountOpen PDF

Abstract

Background: Following Nonablative fractional Fraxel laser (NAFL), a well‐established treatment for skin rejuvenation, immediate post‐procedural care is essential to address any potential complications and accelerate the healing process. Aims: To evaluate the efficacy and patient satisfaction of a topical skincare regimen containing vitamin C, vitamin E, and ferulic acid—CE Ferulic serum (CEF) following NAFL treatment in the Chinese population. Methods: In this randomized, investigator‐blinded, split‐face, controlled trial, patients with mild‐to‐moderate facial photodamage were randomized to receive CEF treatment on one side of the face and normal saline (NS) on the other side immediately after the NAFL procedure and daily during the 7‐day follow‐up. The primary endpoint was the change from baseline in erythema score on Day 7, with key secondary endpoints including changes from baseline in erythema index (EI), melanin index (MI), transepidermal water loss, skin hydration, skin sebum content, scabbing, edema, overall patient satisfaction, and post‐procedure pain. Results: In total, 50 patients (female 45/50) were enrolled in this study, with a mean age of 31.6 years. The mean change from baseline in erythema score was significantly lower on the CEF side than on the NS side on Day 7 post‐NAFL treatment (0.04 ± 0.40 vs. 0.18 ± 0.48, p = 0.011). The CEF side also exhibited improved changes in EI, MI, and skin hydration, as well as higher overall satisfaction and less pain compared with the NS side. Conclusions: Applying CEF after NAFL treatment reduced erythema progression, maintained skin hydration, and promoted the healing process compared with NS. Trial Registration: Chinese Clinical Trial Registry: ChiCTR2300069246

AI snapshot

Written from the paper’s full text.

TL;DR

In a randomized, investigator-blinded, split-face trial of 50 Chinese patients with facial photodamage, topical CE Ferulic serum (CEF) applied after nonablative fractional Fraxel laser treatment reduced erythema progression and improved some barrier-related measures versus normal saline. CEF also yielded higher patient satisfaction and less post-procedure pain, with no product-related adverse events reported.

Key findings

  • Primary endpoint: mean change from baseline in erythema score on Day 7 was significantly lower on the CEF side than the NS side (0.04 ± 0.40 vs. 0.18 ± 0.48, p = 0.011).
  • CEF side showed better mean percentage change from baseline in erythema index on Day 7 (−4.05% ± 22.12% vs. 5.72% ± 20.41%, p < 0.001) and in melanin index on Day 3 (between-group difference −7.16% ± 17.15%, p = 0.005).
  • Skin hydration improved more on the CEF side on Day 1 (difference 9.53% ± 24.37%, p = 0.007) and Day 3 (difference 11.80% ± 24.94%, p = 0.002); TEWL, sebum, edema, and scabbing detachment showed no significant between-side differences.
  • Patients reported less pain on the CEF side at 30 min (3.62 ± 1.37 vs. 4.02 ± 1.15, p = 0.036) and 1 h (1.84 ± 1.27 vs. 2.22 ± 1.09, p = 0.022); 49% (24/49) thought CEF exceeded expectations and no one thought it was below expectations, while 4.1% (2/49) thought NS did not meet expectations.

Methods

  • Randomized, investigator-blinded, split-face, controlled trial in patients aged 18–65 with Fitzpatrick skin type II–IV and mild-to-moderate facial photodamage; 50 patients enrolled (45/50 female; mean age 31.6 ± 7.2 years).
  • After Fraxel DUAL 1550/1927 laser treatment on both sides, patients applied CEF (15% vitamin C, 1% vitamin E, 0.5% ferulic acid) to one randomly assigned side and 0.9% normal saline to the other immediately post-procedure and daily for 7 days.
  • Primary endpoint was change from baseline in erythema score on Day 7; secondary endpoints included erythema index, melanin index, TEWL, skin hydration, sebum, scabbing, edema, satisfaction, and VAS pain. Analyses used paired t-tests or Wilcoxon signed-rank tests for continuous variables, chi-squared tests for categorical variables, and Wilcoxon signed-rank or Cochran’s and Mantel–Haenszel statistics for ordinal variables, with alpha < 0.05.

Limitations

  • Stated in the paper: patients were unblinded for satisfaction and pain assessment, which may have influenced their judgments.
  • Stated in the paper: adherence and application techniques may have varied among individuals despite efforts to monitor adherence, and participants received only one Fraxel laser session, so long-term effectiveness across a full treatment course was not examined.
  • Evident in the text: despite randomization, baseline erythema index was higher on the NS side than the CEF side (249.65 ± 57.59 vs. 245.33 ± 58.02, p = 0.036), and satisfaction data were available for 49 of 50 patients on Day 7.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1111/jocd.70251

Cites

22 of 22 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

5 of 23 cited sources checked · 4 supported · 0 flagged · accuracy not yet measured

  • Interpretationcitation

    The observation of milder pain with CEF could be attributed to the analgesic effect of vitamin C.

    “This observation could be attributed to the analgesic effect of vitamin C [19].”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [19] A. C. Carr and C. McCall, “ The Role of Vitamin C in the Treatment of Pain: New Insights,” Journal of Translational Medicine 15 (2017): 77. 28410599 PMC5391567 source
  • Premisecitation

    Postoperative complications may develop as a result of inflammation and oxidative stress induced by thermal damage from laser treatment.

    “These postoperative complications may develop as a result of inflammation and oxidative stress induced by thermal damage from the laser treatment [9, 10].”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites [9] E. L. Tanzi and T. S. Alster, “ Complications of Ablative and Nonablative Lasers and Light Sources,” in Complications in Cutaneous Surgery, ed. H. M. Gloster (Springer New York, 2008), 10.1007/978-0-387-73152-0_13. source
    • cites [10] J. Chen, Y. Liu, Z. Zhao, and J. Qiu, “ Oxidative Stress in the Skin: Impact and Related Protection,” International Journal of Cosmetic Science 43, no. 5 (2021): 495– 509. 34312881 source

      The UV/visible light/infrared radiation section (page unavailable) says infrared radiation from therapeutic and cosmetic devices can induce reactive oxygen species in skin, supporting the oxidative-stress component. It does not link laser-induced thermal damage to inflammation or postoperative complications. (LLM, conf=0.82)

      Experimental — accuracy not yet measured
  • Premisecitation

    Vitamin C has depigmenting effects by interacting with the enzyme tyrosinase and reducing melanin formation.

    “Additionally, vitamin C is known for its depigmenting effects by interacting with the enzyme tyrosinase and reducing melanin formation [15].”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [15] R. M. Sanadi and R. S. Deshmukh, “ The Effect of Vitamin C on Melanin Pigmentation—A Systematic Review,” Journal of Oral and Maxillofacial Pathology 24, no. 2 (2020): 374– 382. 33456250 PMC7802860 source
  • Findingown data

    More patients were very satisfied with the efficacy of the CEF side than of the NS side (59.2% vs. 46.9%).

    “More patients were very satisfied with the efficacy (CEF: 59.2% vs. NS: 46.9%) and comfort (CEF: 53.1% vs. NS: 38.8%) of the CEF side than that of the NS side.”
    Quote in the paperSubstantial claim
  • Findingown data

    Throughout the 7-day follow-up, the erythema score was lower on the CEF side than on the NS side.

    “Throughout the 7‐day follow‐up, the erythema score was lower on the CEF side than on the NS side (Figure 2a).”
    Quote in the paperSubstantial claim
  • May combine two claims. 13
  • Classified as probably not a substantial claim. 12

  • May combine two claims.

    Premisecitation

    Vitamin C is believed to reduce pro-inflammatory mediators that trigger pain and may be involved in neuromodulation as a cofactor in the synthesis of neurotransmitters.

    “While the mechanisms remain unclear, vitamin C is believed to reduce pro‐inflammatory mediators that trigger pain and may be involved in neuromodulation as a cofactor in the synthesis of neurotransmitters [19].”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [19] A. C. Carr and C. McCall, “ The Role of Vitamin C in the Treatment of Pain: New Insights,” Journal of Translational Medicine 15 (2017): 77. 28410599 PMC5391567 source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Beneficial effects in improved skin hydration following topical application of ferulic acid have been reported.

    “Beneficial effects were also reported in terms of improved skin hydration following the topical application of ferulic acid [17, 18].”
    Quote in the paperNot a substantial claim1 of 2 sources checked
    • cites [17] K. Zduńska‐Pęciak, R. Dębowska, A. Kołodziejczak, and H. Rotsztejn, “ Ferulic Acid—A Novel Topical Agent in Reducing Signs of Photoaging,” Dermatologic Therapy 35, no. 7 (2022): e15543. 35486440 source
    • cites [18] K. Zduńska‐Pęciak, A. Kołodziejczak, and H. Rotsztejn, “ Two Superior Antioxidants: Ferulic Acid and Ascorbic Acid in Reducing Signs of Photoaging—A Split‐Face Comparative Study,” Dermatologic Therapy 35, no. 2 (2022): e15254. 34877760 source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingown data

    There was a trend of reduction in edema score throughout the follow-up period.

    “In terms of edema score, there was a trend of reduction throughout the follow‐up period.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The CEF side showed a lower percentage increase in transepidermal water loss (TEWL) compared to the NS side over the 7-day follow-up, although no significant differences were observed.

    “The CEF side showed a lower percentage increase in TEWL compared to the NS side over the 7‐day follow‐up, although no significant differences were observed.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Among 49 patients who completed the satisfaction questionnaire on Day 7, 49% (24/49) thought the outcome of the CEF side exceeded their expectations and no one thought it was below their expectations.

    “Among them, 49% (24/49) of the patients thought the outcome of the CEF side exceeded their expectations and no one thought it was below their expectations, while 4.1% (2/49) of the patients thought the outcome of the NS side did not meet their expectations.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Asian skin has more melanocytes and tends to produce more melanin, making this population more susceptible to pigmentation disorders.

    “Given that Asian skin has more melanocytes and tends to produce more melanin, making this population more susceptible to pigmentation disorders, it is essential to employ this integrated skincare approach to optimize the effectiveness and minimize the complications of NAFL treatment in this population [21].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [21] I. L. Chan, S. Cohen, M. G. da Cunha, and L. C. Maluf, “ Characteristics and Management of Asian Skin,” International Journal of Dermatology 58, no. 2 (2019): 131– 143. 30039861 source

  • May combine two claims.

    Premisecitation

    The safety profile of CEF has been confirmed, showing good tolerance with immediate use after ablative fractional resurfacing procedures.

    “Furthermore, the safety profile of CEF has been confirmed, showing good tolerance with immediate use after ablative fractional resurfacing procedures [13].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [13] H. Johnson, T. Kazemi, and R. S. Farah, “ Safety Profile of Laser‐Assisted Drug Delivery of Vitamin C, E, and Ferulic Acid Serum Following Ablative Fractional Resurfacing: A Retrospective Chart Review,” Journal of Cosmetic and Laser Therapy 23, no. 7–8 (2021): 207– 208. 35290149 source

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Fraxel laser treatment showed significant improvements in both pigmentation and wrinkles from baseline, with an overall low risk of adverse events.

    “In a retrospective study reviewing 730 patients with diverse skin types and ethnic backgrounds, Fraxel laser treatment showed significant improvements in both pigmentation and wrinkles from baseline, with an overall low risk of adverse events [5]”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [5] S. R. Cohen, A. Goodacre, S. Lim, et al., “ Clinical Outcomes and Complications Associated With Fractional Lasers: A Review of 730 Patients,” Aesthetic Plastic Surgery 41, no. 1 (2017): 171– 178. 28032173 source

  • Classified as probably not a substantial claim. May combine two claims.

    Study design and conductnone given

    Participants in this study received only one session of Fraxel laser treatment, whereas this treatment usually requires several sessions in clinical practice.

    “In addition, participants in this study received only one session of Fraxel laser treatment, whereas this treatment usually requires several sessions in clinical practice.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    Antioxidants have demonstrated effectiveness in managing inflammation and mitigating postoperative oxidative stress by neutralizing oxygen radicals.

    “Antioxidants have demonstrated effectiveness in managing inflammation and mitigating postoperative oxidative stress by neutralizing oxygen radicals [11, 12].”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [11] T. S. Alster and T. B. West, “ Effect of Topical Vitamin C on Postoperative Carbon Dioxide Laser Resurfacing Erythema,” Dermatologic Surgery 24, no. 3 (1998): 331– 334. 9537007 source
    • cites [12] J. Kim, J. Kim, Y. I. Lee, A. Almurayshid, J. Y. Jung, and J. H. Lee, “ Effect of a Topical Antioxidant Serum Containing Vitamin C, Vitamin E, and Ferulic Acid After Q‐Switched 1064‐Nm Nd:YAG Laser for Treatment of Environment‐Induced Skin Pigmentation,” Journal of Cosmetic Dermatology 19, no. 10 (2020): 2576– 2582. 32052907 source

  • May combine two claims.

    Study design and conductnone given

    Patients were unblinded for satisfaction and pain assessment, which may influence their judgments.

    “One limitation of this study is that patients were unblinded for satisfaction and pain assessment, which may influence their judgments.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Fraxel laser, featuring two lasers with different wavelengths (1550 nm/1927 nm), is a well-established type of nonablative laser treatment.

    “Fraxel laser, featuring two lasers with different wavelengths (1550 nm/1927 nm), is a well‐established type of nonablative laser treatment [4].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [4] M. H. Gold, “ Update on Fractional Laser Technology,” Journal of Clinical and Aesthetic Dermatology 3, no. 1 (2010): 42– 50. PMC2921736 20725538

  • Classified as probably not a substantial claim.

    Study design and conductnone given

    Independent investigators were blinded when assessing the evaluation indicators based on standardized clinical images.

    “Independent investigators were blinded when assessing the evaluation indicators based on standardized clinical images obtained by the VISIA skin imaging system (Canfield Scientific, USA).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Study design and conductown data

    There were no statistically significant differences between the two groups regarding baseline characteristics, except that the erythema index on the NS side was higher than on the CEF side (249.65 ± 57.59 vs. 245.33 ± 58.02, p = 0.036).

    “There were no statistically significant differences between the two groups regarding baseline characteristics, except that the erythema index on the NS side was higher than on the CEF side (249.65 ± 57.59 vs. 245.33 ± 58.02, p = 0.036) (Table 1).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationcitation

    The minor skin damage caused by NAFL can enhance the absorption of active components in CE Ferulic, leading to a synergistic effect and optimal treatment outcomes.

    “a previous study has indicated a dose‐dependent permeation of CEF in response to increased laser treatment levels, suggesting that the minor skin damage caused by NAFL can enhance the absorption of active components in CE Ferulic, leading to a synergistic effect and optimal treatment outcomes [20].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [20] E. L. Elford, C. Oresajo, V. P. Bedi, and R. G. Geronemus, “Enhanced Skin Permeability of C E Ferulic After CLEAR + BRILLIANT Perméa Laser Treatment,” (2013), https://www.semanticscholar.org/paper/Enhanced‐Skin‐Permeability‐of‐C‐E‐Ferulic‐after‐%2B‐Elford‐Oresajo/247fbb28a4f7e99d0629dd8d08076a9b1b212f83.

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Laser resurfacing technology is a common and effective method to achieve skin rejuvenation through a focal photothermal action, restoring youthful skin.

    “Laser resurfacing technology is a common and effective method to achieve skin rejuvenation through a focal photothermal action, restoring youthful skin [2, 3].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [2] E. P. Tierney, D. J. Kouba, and C. W. Hanke, “ Review of Fractional Photothermolysis: Treatment Indications and Efficacy,” Dermatologic Surgery 35, no. 10 (2009): 1445– 1461. 19686366 source
    • cites [3] T. S. Alster, E. L. Tanzi, and M. Lazarus, “ The Use of Fractional Laser Photothermolysis for the Treatment of Atrophic Scars,” Dermatologic Surgery 33, no. 3 (2007): 295– 299. 17338686 source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductcitation

    The study required a minimum sample size of 50 patients, assuming an effect size of 1 with SD 0.9, significance level 0.05, 80% power, and 20% dropout rate based on a previous publication.

    “The study required a minimum sample size of 50 patients, assuming an effect size of 1 with a standard deviation (SD) of 0.9 for the primary endpoint, a significance level of 0.05, 80% power, and a 20% dropout rate based on the previous publication [14].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [14] J. S. Waibel, Q. S. Mi, D. Ozog, et al., “ Laser‐Assisted Delivery of Vitamin C, Vitamin E, and Ferulic Acid Formula Serum Decreases Fractional Laser Postoperative Recovery by Increased Beta Fibroblast Growth Factor Expression,” Lasers in Surgery and Medicine 48, no. 3 (2016): 238– 244. 26612341 source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    All patients completed the full course of treatment and follow-up.

    “All patients completed the full course of treatment and follow‐up.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    The lasers create microthermal zones in the skin and stimulate the repair process to promote the synthesis of collagen, thereby achieving the purpose of skin tissue remodeling.

    “The lasers create microthermal zones in the skin and stimulate the repair process to promote the synthesis of collagen, thereby achieving the purpose of skin tissue remodeling [2].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [2] E. P. Tierney, D. J. Kouba, and C. W. Hanke, “ Review of Fractional Photothermolysis: Treatment Indications and Efficacy,” Dermatologic Surgery 35, no. 10 (2009): 1445– 1461. 19686366 source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    There is potential for variation in adherence and application techniques among individuals.

    “Another limitation is the potential for variation in adherence and application techniques among individuals, despite the various approaches we have implemented to enhance adherence.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Study design and conductown data

    Patients were randomly assigned using a random number table to apply CEF on one side of the face and normal saline on the other side in a 1:1 ratio.

    “Following the laser treatment, patients were randomly assigned using a random number table to apply CEF (intervention) on either the left or right side of the face in a 1:1 ratio, and to apply 0.9% normal saline (NS; control) on the other side of the face, immediately after the procedure and after their daily morning routine skincare during the 7‐day follow‐up.”
    Quote in the paperSubstantial claim
21 of 21

  • The paper relies on this without support.

    This is the first trial to provide clinical evidence among Chinese patients with facial photodamage using CEF serum after NAFL.

    “This is the first trial to provide clinical evidence among Chinese patients with facial photodamage using CEF serum after NAFL.”
1 of 1

Cites

Flagged first, then by citations

Research works printed but not linked: 1

  1. E. L.Elford C.Oresajo V. P.Bedi andR. G.Geronemus “Enhanced Skin Permeability of C E Ferulic After CLEAR + BRILLIANT Perméa Laser Treatment ” (2013) https://www.semanticscholar.org/paper/Enhanced‐Skin‐Permeability‐of‐C‐E‐Ferulic‐after‐%2B‐Elford‐Oresajo/247fbb28a4f7e99d0629dd8d08076a9b1b212f83.

Cited by

Still being checked.

Related

Authors
Qin, X., Zhai, J., Zhou, C., Wang, Y., Chen, M., Zhu, L., Shi, Q., Chen, W., Zhang, L., Luo, X., & Li, K.
Affiliations
  • Deyue Clinic Shenzhen China
  • Dexi Cosmetic Clinic Deyi Skin Institution Xi'an China
Corresponding author
Li, Kai
ORCID
Venue
Journal of Cosmetic Dermatology
Publisher
Wiley
Published
2025-05
Volume
24
Issue
5
Pages
e70251-e70251
ISSN
  • 1473-2130 (ISSN-L)
  • 1473-2165
DOI
10.1111/jocd.70251
PMC
PMC12104010
OpenAlex
W4410722795
Semantic Scholar
878b7d1d2e87f82d85598b8dee59d5edbf97848f
Cited by
3
References
22
Citations by year
2026: 3
FWCI
2.39
Type
journal article
Language
en
Open access
Licence
Locations
  • Journal of Cosmetic Dermatology (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • Europe PMC (PubMed Central) (submittedVersion, cc-by)
  • PubMed Central (submittedVersion, cc-by)
Topics
  • Health Sciences › Medicine › Dermatology › Dermatologic Treatments and Research
  • Health Sciences › Medicine › Dermatology › Skin Protection and Aging
  • Health Sciences › Medicine › Dermatology › Facial Rejuvenation and Surgery Techniques
Keywords
ferulic acid, vitamin C, vitamin E, post-procedural care, photodamage, erythema, skin hydration, skin rejuvenation, patient satisfaction, transepidermal water loss, melanin index, scabbing, edema, post-procedural pain
MeSH terms
East Asian People, Adult, Ascorbic Acid, China, Cosmetic Techniques, Coumaric Acids, Erythema, Face, Female, Humans, Male, Middle Aged, Rejuvenation, Skin, Vitamin E, Skin Aging, Single-Blind Method, Treatment Outcome, Patient Satisfaction, Lasers, Solid-State

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-26.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-26.

Cited sources are checked by gpt-6-sol.

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

What counts as a claim ›How we measure confidence ›How we check this ›

Are you an author, or do you see a problem with this page? Request a review