ISBN 3540085238 books & textbook
The Deficiency Index Problem for Powers of Ordinary Differential Expressions (Lecture Notes in Mathematics, 621)
Kauffman, Robert M. Zettl, Anton Read, Thomas T.
Springer /1977-11-01 Paperback / 118 Pages
isbn-10: 3540085238 / isbn-13: 9783540085232
