Seminar or discussion of mixed models helpful, in either R or SAS. Something at the level of Littell RC, Pendergast J, Natarajan R. Modelling covariance structure in the analysis of repeated measures data. Stat Med. 2000 Jul 15;19(13):1793-819. Review. PMID: 10861779 [PubMed - indexed for MEDLINE] - DavidAirey 26 Apr 2004