2Stevenson D L. Trend-surface analysis of the structure of the Ste [ C ]. Genevieve limestone in the Efllngham, Illi- nois area. Urbana: Illinois State Geological Survey, 1970.
3Mccullagh M J. Trend surface analysis [ M ]//The free for- mat function. Nottingham : University of Nottingham, 1973 : 62.
4Unwin D. An introduction to trend surface analysis [ M ]. Norwich : Geo Abstracts Ltd, 1975.
