 as virgins' [...] Other research, especially research looking into virginity loss, reports that 35% of virgins, defined as people who have never engaged in vaginal intercourse, have nonetheless engaged in one or more other forms of heterosexual sexual activity (e.g., oral sex, anal sex, or mutual masturbation).↑ Michael Kent (2000). Advanced biology. Oxford University Press. pp. 250–253. ISBN 978-0199141951. සම්ප්‍රවේශය October 21, 2015.↑ Showick Thorpe; Edgar Thorpe (2009). The Pearson General Studies Manual 2009, 1/e. Pearson Education India. p. 1.79. ISBN 978-8131721339. සම්ප්‍රවේශය October 21, 2015.↑ *Motivation: Theory, Research, and Application. Cengage Learning. 2012. p. 24. ISBN 978-1285401515.Bailey NW, Zuk M (August 2009). "Same-sex sexual behavior and evolution". Trends Ecol. Evol. 24 (8): 439–46. doi:10.1016/j.tree.2009.03.014. PMID 19539396.↑ Balcombe, Jonathan (2006). Pleasurable Kingdom: Animals and the Nature of Feeling Good. Palgrave Macmillan. pp. [00"00"00"