„[Vickery in his handbook of procedures for making, writes that organizing a field into facets] can be achieved only by a detailed examination of the literature of the field“
— Brian Campbell Vickery
Brian Campbell Vickery (1970) Faceted Classification: A Guide to Construction and Use of Special Schemes. p. 20 as cited in: Claire Beghtol (1986) " Semantic Validity: Concepts of Warrant in Bibliographic Classification Systems http://downloads.alcts.ala.org/lrts/lrtsv30no2.pdf" Library Resources & Technical Services. Vol 30. p. 113.