https://bmcsurg.biomedcentral.com/articles/10.1186/s12893-015-0089-y
https://bmcsurg.biomedcentral.com/articles/10.1186/s12893-015-0094-1
https://bmcsurg.biomedcentral.com/articles/10.1186/s12893-015-0092-3
https://bmcsurg.biomedcentral.com/articles/10.1186/s12893-015-0091-4