517.38
Bell 
D 
Bellamn , Richar   Ernest , 1920-
Differential -differential  equation   [by] 
Richar  Bellmas  [and]    Kenneth  L. Cooke  . New   York , Academia   Preees , 1963.
462  P.   24 CM   (Mathematics  in  science  and  engineering, v.6)
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