1. Leutritz, J., Bell Syst. Tech. J., 25, 102 (1946).
2. Gersonde, M., Holtzforschung, 12, 11 (1958).
3. Gersonde, M., Holtzforschung, 12, 104 (1958).
4. Henningsson, B., Studia Forestalia Suecica, 34 (1965).
5. Wilcox, W. W., US Forest Service Research Paper FPL 70 (US Dept. of Agriculture, Forest Products Lab., Madison, Wisconsin, 1968).