MR0168962 Harris, Jr., W. A. and Turrittin, H. L. W. A. HARRIS, Jr. and H. L. TURRITTIN Funkcialaj Ekvacioj. Serio Internacia 6 1964 37--46 http://fe.math.kobe-u.ac.jp/FE/Free/vol06/fe06-3.pdf http://fe.math.kobe-u.ac.jp/FE/FE_pdf_with_bookmark/FE01-10-en_KML/fe06-037-046/fe06-037-046.pdf http://www.ams.org/mathscinet-getitem?mr=MR0168962 fe06-037-046 1964 HARRIS, W. A. Jr.; TURRITTIN, H. L. HARRIS, W. A. Jr.; TURRITTIN, H. L. 1 Bieberbach, L. Lehrbuch der Funktionentheorie B. G. Teubner, Leipzig und Berlin, 1 1930 Data is not found in MathSci. Cache/Bi/Bieberbach,Funktionentheorie,,*,1930,1931

2 Harris, W. A. Jr. Contributions to Differential Equations 1 1963 489-518 MR0147801 100 Cache/Ha/Harris,difference,Contributions*,1963,1964

3 Harris, W. A. Jr., Equivalent classes of difference equations, Contributions to Differential Equations (to appear) MR0150490 4 Milne-Thomson, L. M. The calculus of finite differences MacMillan and Co., London 1951 MR0043339 Cache/Mi/Milne-Thompson,differences,,*,1951,1952

5 Nielsen, N. Rendiconti della R. Acc. dei Lincei (5) 13 1904 517-524 Data is not found in MathSci. Cache/Ni/Nielsen,multiplication,Rendiconti*,1904,1905

6 Nörlund, N. E. Leçons sur les séries d' interpolation Gauthiers-Villars et Cie, Paris 1926 Data is not found in MathSci. Cache/No/N\"orlund,interpolation,,*,1926,1927