Flexible surrogate marker evaluation from several randomized clinical trials with continuous endpoints, using R and SAS. - Abel Tilahun; Assam Pryseley; Ariel Alonso Abad; Geert Molenberghs (Comput. Stat. Data Anal., 2007)

Using earlier measures in a longitudinal sequence as a potential surrogate for a later one. - Assam Pryseley; Abel Tilahun; Ariel Alonso Abad; Geert Molenberghs (Comput. Stat. Data Anal., 2010)

Estimating negative variance components from Gaussian and non-Gaussian data: A mixed models approach. - Assam Pryseley; Clotaire Tchonlafi; Geert Verbeke; Geert Molenberghs (Comput. Stat. Data Anal., 2011)