1. Oliver, J. E.: 1973,Climate and Man's Environment, John Wiley, New York, pp. 169–191.
2. Critchfield, H. J.: 1960,General Climatology, Prentice-Hall, Englewood Cliffs, N.J., p. 165.
3. Russell, R. J.: 1932,Univ. of California Publs. in Geogr.
5.
4. Russell, R. J.: 1934,Geogr. Rev.
24, 92.
5. Bowman, I.: 1935,Geogr. Rev.
25, 43.