3 literature references for Pterobryella rigida Touw, 1971:

Author: Crosby, M. R. and others - USED
Year: 1999
Title: USED in a checklist or nondescriptive flora, citing collections, since 1963
Source: Checklist Mosses
Author: Brotherus & Irmscher
Year: 1914
Title:
Source: Mem. Soc. Sci. Nat. Neuchatel
Author: Touw
Year: 1971
Title:
Source: Blumea