31. randomised controlled trial.pt.
32. controlled clinical trial.pt.
33. (clinical trial or clinical trial phase i or clinical trial phase ii or clinical trial phase iii or clinical trial phase iv).pt.
34. multicenter study.pt.
35. (evaluation studies or comparative study).pt.
36. random$.tw.
37. (controlled adj5 (trial$ or stud$)).tw.
38. (clinical$ adj5 trial$).tw.
39. ((control or treatment or experiment$ or intervention) adj5 (group$ or subject$ or patient$)).tw.
40. (quasi-random$ or quasi random$ or pseudo-random$ or pseudo random$).tw.
41. ((multicenter or multicentre or therapeutic) adj5 (trial$ or stud$)).tw.
42. ((control or experiment$ or conservative) adj5 (treatment or therapy or procedure or manage$)).tw.
43. ((singl$ or doubl$ or tripl$ or trebl$) adj5 (blind$ or mask$)).tw.
44. (coin adj5 (flip or flipped or toss$)).tw.
45. versus.tw.