G. Weidner and W. Griffitt, "Rape: A Sexual Stigma", Journal of Personality (1983), see p. 159.

For more info on the questionnaire used in this study to measure attitudes towards porn and sex, see:

William Fisher, Donn Byrne, Leonard White, and Kathryn Kelley, "Erotophobia-Erotophilia as a Dimension of Personality", Journal of Sex Research Vol. 25, No. 1 (February 1988).