2 literature references for Hygrotus marklini (Gyllenhal, 1813):

Author: Nilsson, Anders N.
Year: 2001
Title:
Source: World Catalogue of Insects, volume 3: Dytiscidae (Coleoptera)
Author: Larson, D. J., Y. Alarie, and R. E. Roughley
Year: 2000
Title:
Source: Predaceous Diving Beetles (Coleoptera: Dytiscidae) of the Nearctic Region, with emphasis on the fauna of Canada and Alaska