Book reviews: Adams,G. F.,editor,I975: Planation surfaces. Benchmark Papers in Geology,22. Strouds burg,Pennsylvania: Dowden,Hutchinson and Ross. UK distributors: John Wiley. xv+476 pp. $3I.30 (£I8.45)

Davis, W.M. 1889: The rivers and valleys of Pennsylvania. National Geographic Magazine I, 183-253.

Gilbert, G.K. 1909: The convexity of hill-tops. Journal of Geology 17, 344-50.

Horton, R.E. 1945: Erosional development of streams and their drainage basins: hydrographical approach to quantitative morphology. Bulletin of the Geological Society of America 56, 275-370.

Lustig, L.K. 1969: Trend surface analysis of the Basin and Range province and some geomorphic implications. US Geological Survey , professional paper, 500-D.

Paige, S. 1912: Rock-cut surfaces in the desert ranges. Journal of Geology 20, 442-50.

Penck, W. , 1924. Die morphologische analyse. Stuttgart (translated by H. Czech and K. C. Boswell), 1953, Morphological analysis of landforms. London: Macmillan , and New York: St Martin's Press.

Powell, J.W. 1875: Exploration of the Colorado River of the West. Washington.

Ramsay, A.C. 1846: The denudation of South Wales and adjacent English counties . Memoirs of the Geological Survey of Great Britain .

Strahler, A.N. 1950: Equilibrium theory of erosional slopes approached by frequency distribution analysis. American Journal of Science 248, 673-96, 800-14.