https://bmcmedresmethodol.biomedcentral.com/articles/10.1186/1471-2288-14-114
https://bmcmedresmethodol.biomedcentral.com/articles/10.1186/1471-2288-14-116
https://bmcmedresmethodol.biomedcentral.com/articles/10.1186/1471-2288-14-113
https://bmcmedresmethodol.biomedcentral.com/articles/10.1186/1471-2288-14-115
https://bmcmedresmethodol.biomedcentral.com/articles/10.1186/1471-2288-14-117