446 Iturnoris NaTurAL History Survey BULLETIN Vol. 26, Art. 5 
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1945. Flora of Illinois. [A review of a book with that title.] Science, n.s., 102(2656) :542-3. 
1949. Minimum areas for different vegetations: Their determination from species-area 4 
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Vestal, A. G., and H. Bartholomew 
1941. Prairie of loess bluffs of the Illinois River. (Abs.) Ecol. Soc. Am. Bul. 22(4) :41. 
Vestal, Arthur G., and Mary Frances Heermans 
1945. Size requirements for reference areas in mixed forests. Ecology 26(2) : 122-34. 
Woodard, John 
1924. Origin of prairies in Illinois. Bot. Gaz. 77(3) :241-61. 
Worthen, A. H. 
1868. Geological survey of Illinois. Vol. 3. Geology and palaeontology. [Illinois Geological 
Survey, Springfield.] 574 pp. 
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