Perleth, Christoph; Schatz, Tanja; Mönks, Franz J. (2000). «Early Identification of High Ability». En Kurt A. Heller; Franz J. Mönks; Robert J. Sternberg et al., eds. International Handbook of Giftedness and Talent (2ª edición). Amsterdam: Pergamon. p. 301. ISBN978-0-08-043796-5. «norm tables that provide you with such extreme values are constructed on the basis of random extrapolation and smoothing but not on the basis of empirical data of representative samples.»Se sugiere usar |número-editores= (ayuda)