RT Journal Article SR Electronic T1 Health research among hard-to-reach people: six degrees of sampling JF Canadian Medical Association Journal JO CMAJ FD Canadian Medical Association SP 1145 OP 1149 DO 10.1503/cmaj.141076 VO 187 IS 15 A1 Aglipay, Mary A1 Wylie, John L. A1 Jolly, Ann M. YR 2015 UL http://www.cmaj.ca/content/187/15/1145.abstract AB