Haviland, A., Jones, B., & Nagin, D. (2011). Group-based Trajectory Modeling Extended to Account for Nonrandom Participant Attrition Sociological Methods & Research, 40 (2), 367-390 DOI: 10.1177/0049124111400041
Daniel S. Nagin, Carnegie Mellon University, Pittsburgh, PA, USA, dn03@andrew.cmu.edu