論文（英文）
Estimation of treatment effect adjusting for treatment changes using the intensity score method: application to a large primary prevention study for coronary events (MEGA study).
Tanaka Y, Matsuyama Y, and Ohashi Y. for the MEGA Study Group. Estimation of treatment effect adjusting for treatment changes using the intensity score method: an application to a large primary prevention study for coronary events (MEGA study). Statistics in Medicine 2008; 27:1718-1733.