https://bmcsurg.biomedcentral.com/articles/10.1186/s12893-016-0194-6
https://bmcsurg.biomedcentral.com/articles/10.1186/s12893-016-0197-3
https://bmcsurg.biomedcentral.com/articles/10.1186/s12893-016-0198-2
https://bmcsurg.biomedcentral.com/articles/10.1186/s12893-016-0196-4