Identification of research studies
Potential research studies were identified through four methods. First, published research articles were identified via a search of the PsycINFO and  IAP Reference databases. Second, unpublished doctoral dissertations were located through the ProQuest Digital Dissertations database.
Search keywords included Cattell-Horn-Carroll, CHC theory, CHC, Gf-Gc theory, Gf- Gc, Woodcock- Johnson-Revised, WJ-R, Woodcock-Johnson III, WJ III, Kaufman Assessment Battery for Children—Second Edition, KABC-II, Differential Abilities Scales, DAS, Differential Abilities Scales—Second Edition (DAS-II), Stanford- Binet—Fifth Edition, and SB-IV. Years included in the searches spanned 1988 to 2009.
Third, a request was posted to the Cattell-Horn-Carroll (CHC) and the National Association of School Psychologists (NASP) general purpose listservs asking members for copies of published and unpublished manuscripts or references related to the review. Finally, an ancestral search involved examination of the references of the initial research reports (acquired during the first three steps) to determine if they contained references to studies not revealed by the primary search strategy that should be secured for review (Cooper, 1998).