19. https://www.ncbi.nlm.nih.gov/pubmed/11581442
20. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3374237
21. https://www.ncbi.nlm.nih.gov/pubmed/26178720
22. https://www.ncbi.nlm.nih.gov/pubmed/19640952
23. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2868080
24. https://www.ncbi.nlm.nih.gov/pubmed/19400750
25. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1334192
26. https://www.ncbi.nlm.nih.gov/pubmed/21656330
27. https://www.ncbi.nlm.nih.gov/pubmed/20645852
28. https://www.ncbi.nlm.nih.gov/pubmed/21983804
29. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2716748
30. https://www.ncbi.nlm.nih.gov/pubmed/16180224
31. https://www.ncbi.nlm.nih.gov/pubmed/16871438
32. https://www.ncbi.nlm.nih.gov/pubmed/23632752
33. https://www.ncbi.nlm.nih.gov/pubmed/16505339
34. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2633336
35. https://www.ncbi.nlm.nih.gov/pubmed/20687386
36. https://www.ncbi.nlm.nih.gov/pubmed/17971178
37. https://www.ncbi.nlm.nih.gov/pubmed/18370662
38. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2367001