RESEARCH AND DEVELOPMENT NEEDS IN DATA COLLECTION FOR ROCK ENGINEERING.STEFFEN OKH.1976; IN: EXPLOR. ROCK ENG. PROC. SYMP. EXPLOR. ROCK ENG.; JOHANNESBURG; 1976; CAPE TOWN; A.A. BALKEMA; DA. 1976; VOL. 2; PP. 93-104; BIBL. 22 REF.; 10 ILL.Conference Paper

RECENT DEVELOPMENTS IN THE INTERPRETATION OF DATA FROM JOINT SURVEYS IN ROCK MASSES.STEFFEN OKH; KERRICH JE; JENNINGS JE et al.sdIN: SOIL MECH. FOUND. ENG. 6. REG. CONF. AFRICA. PROC.; DURBAN; 1975; CAPE TOWN A.A.BALKEMA,1976, VOL. 2, P. 17 A 26Miscellaneous