Németh, A.B. “A Geometrical Approach to Conjugate Point Classification for Linear Differential Equations”. Anal. Numér. Théor. Approx. 4, no. 2 (August 1, 1975): 137–152. Accessed November 24, 2024. https://ictp.acad.ro/jnaat/journal/article/view/1975-vol4-no2-art4.