title: Mathematical coupling: a multilevel approach.
authors.affiliation: Biostatistics Unit, Centre for Epidemiology and Biostatistics, Leeds Institute of Genetics, Health & Therapeutics, University of Leeds, Leeds LS2 9LN, UK. m.s.gilthorpe@leeds.ac.uk
authors.forename: Mark S
authors.initials: MS
authors.lastname: Gilthorpe
authors.forename: Yu-Kang
authors.initials: YK
authors.lastname: Tu
mesh_terms: D015982:Bias; D015340:Epidemiologic Research Design; D006801:Humans; D008433:Mathematics