1.	Randomized Controlled Trial/
2.	controlled study/
3.	clinical study/
4.	major clinical study/
5.	prospective study/
6.	meta analysis/
7.	exp clinical trial/
8.	randomization/
9.	crossover procedure/ or double blind procedure/ or parallel design/ or single blind procedure/
10.	Placebo/
11.	latin square design/
12.	exp comparative study/
13.	follow up/
14.	pilot study/
15.	family study/ or feasibility study/ or pilot study/ or study/
16.	placebo$.tw.
17.	random$.tw.
18.	(clin$ adj25 trial$).tw.
19.	((singl$ or doubl$ or trebl$ or tripl$) adj25 (blind$ or mask$)).tw.
20.	factorial.tw.
21.	crossover.tw.
22.	latin square.tw.
23.	(balance$ adj2 block$).tw.
24.	or/1‐23
25.	(nonhuman not human).sh.
26.	24 not 25
27.	factorial design/
28.	parallel design/
29.	triple blind procedure/
30.	community trial/
31.	intervention study/
32.	experimental study/
33.	prevention study/
34.	quasi experimental study/
35.	or/27‐34
36.	24 or 35
37.	36 not 25
38.	urethra stricture/
39.	urethra stenosis/
40.	(urethra$ adj5 (stricture$ or stenos$)).tw.
41.	(urethra$ adj5 narrow$).tw.
42.	41 or 38 or 39 or 40
43.	urethroplasty/ or urethrotomy/
44.	urethroplast$.tw.
45.	urethrotom$.tw.
46.	dilatat$.tw.
47.	intermittent catheterization/
48.	catheter$.tw.
49.	bladder catheterization/ or urethral catheterization/
50.	49 or 46 or 45 or 43 or 44 or 48 or 47
51.	42 and 50 and 37