The books' attitudes towards minority characters are a matter of disagreement. These early volumes have been called models of diversity for their day, since among the Hardys' friends are Phil Cohen, who is Jewish, and the Italian immigrant Tony Prito. However, these two friends are rarely involved in the Hardys' adventures, a level of friendship reserved for Biff Hooper and Chet Morton. The books have been extensively criticized for their use of racial and ethnic stereotypes and their xenophobia. Vilnoff, for example, the villain in "The Sinister Sign-Post" (1936), is described as "swarthy" and "a foreigner", notes critic Steve Burgess.