1. Hutchinson, H. B. and Richards, E. H., Artificial farmyard manure. J. Ministr. Agr.28, 398 (1921).
2. Norman, A. G., Microbial thermogenesis. Iowa Agr. Exp. Sta. Ann. Rept. 1939 p. 76.
3. Carlyle, R. E. and Norman, A. G., Microbial thermogenesis in the decomposition of plant materials. J. Bact.41, 699 (1941).
4. Demolon, A. and Burgevin, H., Practical instructions for the manufacture of artificial manure. J. Agr. prat.96, 192?193 (1932).
5. Hesse, W. und Schmalfuss, K., Einige Untersuchungen über Kunstmist. Bodenk. und Pflanzenernähr.8, 355?373 (1938).