Gay and Bisexual Men Who Trade Sex for Money, Goods, or Drugs in Vancouver, Canada. (1st May 2017) - Armstrong, Heather L.; Lachowsky, Nathan J.; Wang, Lu; Zhu, Julia; Taylor, Matthew; Rich, Ashleigh J.; Card, Kiffer G.; Olarewaju, Gbolahan; Hogg, Robert S.; Moore, David M.; Roth, Eric A.