title: Research problems and variables.
authors.affiliation: Division of Child Psychiatry, University of Colorado School of Medicine, Denver, USA.
authors.forename: R J
authors.initials: RJ
authors.lastname: Harmon
authors.forename: G A
authors.initials: GA
authors.lastname: Morgan
mesh_terms: D015984:Causality; D002648:Child; D006801:Humans; D012107:Research Design