1. Ahti, T., Hämet-Ahti, L. & Jalas, J. 1968. Vegetation zones and their sections in northwestern Europe. Ann. Bot. Fenn. 5: 169?211.
2. Cajander, A. K. 1909. Ueber Waldtypen. Acta For. Fenn. 1(1): 1?176.
3. Cajander, A. K. 1949. Forest types and their significance. Acta For. Fenn. 56(5): 1?71.
4. Clements, F. E. 1916. Plant succession: an analysis of the development of vegetation. Carnegie Institution of Washington Publication 242: 1?512.
5. Daubenmire, R. 1968. Plant communities: a textbook of plant synecology. 300 p. Harper & Row, New York.