A. Rudén, M. Bäckman, S. Bygdeman, A. Jonsson, O. Ringertz, and E. Sandström, “Gonorrhoea in heterosexual men. Correlation between gonococcal W serogroup, Chlamydia trachomatis infection and objective symptoms”, Acta Derm Venereol, vol. 66, no. 5, pp. 453–456, Sep. 1986.