1. Wolves, brown bears and crows: bounty on killed “harmful birds and bears” during the Meiji Period in Hokkaido;Yamada;Memoirs of the Pioneer Memorial of Hokkaido,2002
2. A research on wintering dens of Ezo-brown bear (Ursus arctos yesoensis Lydekker;Ohkawa;Shin Higuma Tsushin,1979