Such attempts at recovering a sense of historical depth in PIE have been combined with efforts towards linking the history of the language with archaeology, notably with the Kurgan hypothesis. J. P. Mallory's 1989 "In Search of the Indo-Europeans" and 1997 "Encyclopedia of Indo-European Culture" gives an overview of this. Purely linguistic research was bolstered by attempts to reconstruct the culture and mythology of the Proto-Indo-Europeans by scholars such as Georges Dumézil, as well as by archaeology (e. g. Marija Gimbutas, Colin Renfrew) and genetics (e. g. Luigi Luca Cavalli-Sforza). These speculations about the "realia" of Proto-Indo-European culture are however not part of the field of comparative linguistics, but rather a sister-discipline.