1. April, R. H. and Newton, R. M: 1983, Soil Sci. 135, 301.
2. April, R. H. and Newton, R. M.: 1985, Water, Air, and Soil Pollut. 26, 373 (this issue).
3. Braun, E. L.: 1950, Deciduous Forests of Eastern North America. The Free Press, N.Y.
4. Cronan, C. S.: 1979, Anal. Chem. 51, 1333.
5. Cronan, C. S.: 1980, Oikos 34, 272.