TY  - RPRT
TI  - Modelling the random effects covariance matrix in longitudinal data.
AU  - Michael J Daniels
AU  - Yan D Zhao
PY  - 2003
DO  - 10.1002/sim.1470
UR  - https://pubmed.ncbi.nlm.nih.gov/12720301/
ID  - 12720301
ER  -