Appendix 1. Search strategy in PubMed

#22      Search #18 and #19 and #20 and #21

#21      Search #15 or #16 or #17

#20      Search #13 or #14      

#19      Search #8 or #9 or #10 or #11 or #12

#18      Search #1 or #2 or #3 or #4 or #5 or #6 or #7  

#17      Search sexually transmitted infections            

#16      Search AIDS   

#15      Search HIV     

#14      Search prevention       

#13      Search intervention     

#12      Search web     

#11      Search website            

#10      Search cyber   

#9        Search online  

#8        Search Internet            

#7        Search male commercial sex worker   

#6        Search money boy      

#5        Search bisexual men   

#4        Search gay men          

#3        Search homosexual men         

#2        Search MSM   

#1        Search men who have sex with men