The study had been cam 4 implemented in 13 cities that are european. The choice to utilize Time Location Sampling (TLS) or Respondent Driven Sampling (RDS) to recruit participants had been according to preliminary research that is formative. TLS (also referred to as Venue evening Sampling, Temporal Spatial Sampling, and Time Venue Sampling) ended up being utilized to recruit individuals in Brussels, Sofia, Hamburg, Warsaw, Lisbon, Ljubljana, Barcelona, Stockholm, and Brighton (letter = 3596). TLS is a quasi method that is probabilistic to recruit users of a target population at particular times in set venues. 17 In this research, the venues or settings for data collection included social and/or commercial venues and cruising settings preliminarily identified through formative research and that have been then chosen arbitrarily for information collection sampling calendars. 18 RDS had been found in Bratislava, Bucharest, Verona, and Vilnius (letter = 1305).