Integral criteria are established for $\dim V_i(p)=0$ and $\dim V_i(p)=1, i\in \lbrace 0,1\rbrace $, where $V_i(p)$ is the space of solutions $u$ of the equation \[ u^{\prime \prime }+p(t)u=0 \] satisfying the condition \[ \int ^{+\infty }\frac{u^2(s)}{s^i}ds<+\infty \,. \]
@article{107786, author = {T. Chantladze and Nodar Kandelaki and Alexander Lomtatidze}, title = {On quadratically integrable solutions of the second order linear equation}, journal = {Archivum Mathematicum}, volume = {037}, year = {2001}, pages = {57-62}, zbl = {1090.34537}, mrnumber = {1822762}, language = {en}, url = {http://dml.mathdoc.fr/item/107786} }
Chantladze, T.; Kandelaki, Nodar; Lomtatidze, Alexander. On quadratically integrable solutions of the second order linear equation. Archivum Mathematicum, Tome 037 (2001) pp. 57-62. http://gdmltest.u-ga.fr/item/107786/
On the non-existence of conjugate points, Amer. J. Math. 73 (1951), 368–380. (1951) | MR 0042005
Untersuchung und asymptotische Darstellung der Integrale gewisser Differentialgleichungen bei grossen reelen Werten des Arguments, J. Reine Angew. Math. 116 (1896), 178–212.
Asymptotic properties of solutions of nanautonomous ordinary differential equations, Kluwer Academic Publishers, Dordrecht–Boston–London, 1992. (1992)
Singular boundary value problems for second order differential equations, in “Current Problems in Mathematics: Newest Results,” vol. 30, pp. 105–201, Itogi Nauki i Tekhniki, Akad. Nauk SSSR, Vsesoyzn. Inst. Nauchn. i Tekhn. Inform., Moscow, 1987. (1987) | MR 0925830
Oscillation and nonoscillation criteria for second order linear equations, Georgian Math. J. 6 (1999), No 5, 401–414. (1999) | MR 1692963