https://bmcmedresmethodol.biomedcentral.com/articles/10.1186/s12874-020-01161-1 https://bmcmedresmethodol.biomedcentral.com/articles/10.1186/s12874-020-01166-w https://bmcmedresmethodol.biomedcentral.com/articles/10.1186/s12874-020-01157-x https://bmcmedresmethodol.biomedcentral.com/articles/10.1186/s12874-020-01171-z https://bmcmedresmethodol.biomedcentral.com/articles/10.1186/s12874-020-01160-2 https://bmcmedresmethodol.biomedcentral.com/articles/10.1186/s12874-020-01163-z https://bmcmedresmethodol.biomedcentral.com/articles/10.1186/s12874-020-01154-0 https://bmcmedresmethodol.biomedcentral.com/articles/10.1186/s12874-020-01168-8 https://bmcmedresmethodol.biomedcentral.com/articles/10.1186/s12874-020-01173-x https://bmcmedresmethodol.biomedcentral.com/articles/10.1186/s12874-020-01164-y https://bmcmedresmethodol.biomedcentral.com/articles/10.1186/s12874-020-01169-7 https://bmcmedresmethodol.biomedcentral.com/articles/10.1186/s12874-020-01162-0 https://bmcmedresmethodol.biomedcentral.com/articles/10.1186/s12874-020-01148-y https://bmcmedresmethodol.biomedcentral.com/articles/10.1186/s12874-020-01150-4 https://bmcmedresmethodol.biomedcentral.com/articles/10.1186/s12874-020-01155-z https://bmcmedresmethodol.biomedcentral.com/articles/10.1186/s12874-020-01146-0 https://bmcmedresmethodol.biomedcentral.com/articles/10.1186/s12874-020-01153-1 https://bmcmedresmethodol.biomedcentral.com/articles/10.1186/s12874-020-01167-9 https://bmcmedresmethodol.biomedcentral.com/articles/10.1186/s12874-020-01141-5 https://bmcmedresmethodol.biomedcentral.com/articles/10.1186/s12874-020-01149-x