Bibliography (6):

1. Effects of Sexual Activity on Beard Growth in Man

2. Anthropological invariants in travel behavior

3. Feeling Small: Exploring the Tactile Perception Limits

4. A Preliminary Survey of Rhinotillexomania in an Adolescent Sample

5. Wikipedia Bibliography:

   1. Nail (anatomy) § Growth

      https://en.wikipedia.org/wiki/Nail_(anatomy)#Growth

   2. https://en.wikipedia.org/wiki/Nail_(anatomy)

      https://en.wikipedia.org/wiki/Nail_(anatomy)