1. Cowling, E. B., in Cellular Ultrastructure of Woody Plants (edit. by Cote, W. A.), 341 (Syracuse Univ. Press, 1965).
2. Nord, F. F., Sci. Amer., 199, 104 (1958).
3. Cowling, E. B., U.S. Dept. Agric. Tech. Bull., No. 1258, 78 (1961).
4. Wilcox, W. W., Forest Products, 15, 255 (1965).
5. Meier, H., Holz alh Roh- und Werkstoff, 13, 323 (1955).