A comparative study of mentoring among men and women in managerial, professional, and technical positions.
Dreher, George F.;Ash, Ronald A.
Journal of Applied Psychology, Vol 75(5), Oct 1990, 539-546. doi: 10.1037/0021-9010.75.5.539
http://psycnet.apa.org/journals/apl/75/5/539/