Properties of Portland cements obtained by the gypsum-sulphuric acid process /
Wolf, F.
Hille, J.
Garston :  Building Research Station, 
1970.
Originally published as Eigenschaften von Portlandzementen aus dem Gips-Schwefelsaure-Verfahren, in Silikattechnik, 1967, 18(1) 1-8, and (2), 55-7.