[centimeter]

> Do you have a single source to back up these claims?

I have many. You should start with these:

https://www1.udel.edu/educ/gottfredson/30years/Rushton-Jense...

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4270739/pdf/mp2...

[vict7]

Thanks for the source! Just finished the first one.