Molenberghs, G; Njagi, EN; Kenward, MG; Verbeke, G; (2012) Enriched data problems and essential non-identifiability. International journal of statistics in medical research, 1. pp. 16-44. ISSN 1929-6029 https://researchonline.lshtm.ac.uk/id/eprint/2550424 Full text not available from this repository.