論文（英文）
Tanaka S, Matsuyama Y, Ohashi Y. Validation of surrogate endpoints in cancer clinical trials via principal stratification with an application to a prostate cancer trial
Tanaka S, Matsuyama Y, Ohashi Y. Validation of surrogate endpoints in cancer clinical trials via principal stratification with an application to a prostate cancer trial. Stat Med. 2017;36(19):2963-77.