Keyword "NA-RHYOLITE" in:

Early Paleozoic quartz keratophyre on the Malý Bezděz Hill
Fediuk,F., volume 30, 1997 (GRR for 1996), pages 143–145
pdf (0.24 MB)

Recrystallized Ordovician Pitchstones and Perlites in Prague-Troja
Fediuk,F., volume 29, 1996 (GRR for 1995), pages 65–66
pdf (0.08 MB)