# Article

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Summary:
In this article, we consider the operator $L$ defined by the differential expression $\ell (y)=-y^{\prime \prime }+q(x) y ,\quad - \infty < x < \infty$ in $L_2(-\infty ,\infty )$, where $q$ is a complex valued function. Discussing the spectrum, we prove that $L$ has a finite number of eigenvalues and spectral singularities, if the condition $\sup _{-\infty < x < \infty } \Big \lbrace \exp \bigl (\epsilon \sqrt{|x|}\bigr ) |q(x)|\Big \rbrace < \infty , \quad \epsilon > 0$ holds. Later we investigate the properties of the principal functions corresponding to the eigenvalues and the spectral singularities.
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