48 random$.tw.
49 (controlled adj5 (trial$ or stud$)).tw.
50 (clinical$ adj5 trial$).tw.
51 ((control or treatment or experiment$ or intervention) adj5 (group$ or subject$ or patient$)).tw.
52 (quasi-random$ or quasi random$ or pseudo-random$ or pseudo random$).tw.
53 ((multicenter or multicentre or therapeutic) adj5 (trial$ or stud$)).tw.
54 ((control or experiment$ or conservative) adj5 (treatment or therapy or procedure or manage$)).tw.
55 ((singl$ or doubl$ or tripl$ or trebl$) adj5 (blind$ or mask$)).tw.
56 (coin adj5 (flip or flipped or toss$)).tw.
57 versus.tw.
58 (cross-over or cross over or crossover).tw.
59 placebo$.tw.
60 sham.tw.
61 (assign$ or alternate or allocat$ or counterbalance$ or multiple baseline).tw.
62 controls.tw.
63 (treatment$ adj6 order).tw.
64 27 or 28 or 29 or 30 or 31 or 32 or 33 or 34 or 35 or 36 or 37 or 38 or 39 or 40 or 41 or 42 or 43 or 44 or 45 or 46 or 47 or 48 or
49 or 50 or 51 or 52 or 53 or 54 or 55 or 56 or 57 or 58 or 59 or 60 or 61 or 62 or 63
65 26 and 64
66 limit 65 to human