1. Effects of sample purity on discordant mineral ages found in K-Ar dating;Engels;J. Geol.,1971
2. Determination of purity of mineral separates used in K-Ar dating—an interpretive review;Engels;Can. Mineral,1972
3. Effect of sample inhomogeneity in K-Ar dating;Engels;Geochim. Cosmochim. Acta,1970
4. Information Sheets 1 and 2, LP-6 Bio 40–60 mesh;Engels,1971
5. Information Sheets 3–9, LP-6 Bio 40–60 mesh;Engels,1972