https://bmcsurg.biomedcentral.com/articles/10.1186/s12893-016-0148-z
https://bmcsurg.biomedcentral.com/articles/10.1186/s12893-016-0146-1
https://bmcsurg.biomedcentral.com/articles/10.1186/s12893-016-0144-3
https://bmcsurg.biomedcentral.com/articles/10.1186/s12893-016-0149-y
https://bmcsurg.biomedcentral.com/articles/10.1186/s12893-016-0147-0