Ross, Shepley L.
Introduction to ordinary differenstila equations
"New York: John Wiley & Sons, 1981",
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Muller-Pfeiffer, Erich
Spectral theory of ordinary differentials operators
Ellis Horwood, 1981
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Weintraub, Steven H.
Differential forms : theory and practice
Academic Press, 2014
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Coddington, Earl A.
Theory of ordinary differential equations
Tata Mcgraw-Hill, 1982
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Sari Wahyuni
Qualitative Research Method : Theory and Practice
Penerbit Salemba Empat, 2011
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