Vincenzo Nobile et al. 2021. The Effects of the Oral Supplementation with a Natural Keratin Hydrolysate (Kera-Diet®) on Hair and Nails: Randomized, Placebo and Benchmark-Controlled Clinical Trial on Healthy Females. Trichology and Cosmetology – Open Journal. 4, 1 (Jan. 2021), 7–16.