Trois messieurs vêtus de noir

From Author Wars - https://authorwars.com/books/trois-messieurs-vetus-de-noir-1796635.html

Overview:

Title: Trois messieurs vêtus de noir
Author: August Derleth
Year: 1970
Type: Short Fiction

Editions/Publications:

Unknown. Vingt pas dans l'au-delà (Unknown, August Derleth, Casterman, 322 pages, Hardcover, Anthology)
Unknown. L'amulette tibétaine (Unknown, August Derleth, Néo, 208 pages, Trade Paperback, Collection)