V. N. Levchuk
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Articles: 1
On a function system making a basis in a weight space
V. A. Zolotarev, V. N. Levchuk
MFAT 23 (2017), no. 3, 261-269
261-269
We find necessary and sufficient conditions for systems of functions generated by a second order differential equation to form a basis. The results are applied to show that Mathieu functions make a basis.