1. Clinical Trial/

2. Randomized controlled trial/

3. Randomization/

4. Single blind procedure/

5. Double blind procedure/

6. Crossover procedure/

7. Placebo/

8. Randomi?ed controlled trial$.tw.

9. Rct.tw.

10. Random allocation.tw.

11. Randomly allocated.tw.

12. Allocated randomly.tw.

13. (allocated adj2 random).tw.

14. Single blind$.tw.

15. Double blind$.tw.

16. ((treble or triple) adj blind$).tw.

17. Placebo$.tw.

18. Prospective study/

19. or/1‐18

20. Case study/

21. Case report.tw.

22. Abstract report/ or letter/

23. or/20‐22

24. 19 not 23

25. sickle cell.mp.

26. priapism.mp.

27. priapic.mp.

28. erectile.mp.

29. 25 and 26

30. 25 and 27

31. 25 and 28

32. 29 or 30 or 31

33. 24 and 32

34. limit 33 to yr="2016"