[1] Blanton G., Baker J. А.: Iteration groups generated by $C^\ast$ functions. Аrch. Math. (Brno) 3, XVIII, 1982, 121-128. MR 0682099 | Zbl 0518.26002

[2] Borůvka O.: Linear Differential Transformations of the Second Order. The English Univ. Press, London, 1971. MR 0463539

[3] Borůvka O.: Sur les transformations simultanées de deux équations différentielles linéaires du deuxième ordre dans elles-mêmes. Applicable Anal. 1983, 15, No 1-4, 187-200. MR 0710190

[4] Borůvka O.: Sur les sous-groupes planaires des groupes des dispersions des équations différentielles linéaires du deuxième ordre. Proc. Roy. Soc. Edinburgh, 97 A (1984), 35-41. MR 0751175

[5] Borůvka O.: Lectures at the seminar of the Institute of Mathematics of the Czechoslovak Acәdemy of Science in Brno.

[6] Krbiľa J.: Vlastnosti fáz neoscilatorických rovníc y" = q(t)y definovaných pomocou hyperbolických polárných súradnic. Sborník prací VŠD a VUD, Nadas (Praha), 19, (1969), 5-11.

[7] Krbiľa J.: Applikation von parabolischen Phasen der Differentialgleichung y'' = q(t)y. Sborník prací VŠD a VUD, IV. ved. konf., 1.sekcia, 1973, 67-74. MR 0397087

[8] Krbiľa J.: Explicit solutions of several Kummer's nonlinear differential equations. Mat. Čas. 24, 1974, No 4, 343-348. MR 0382767

[9] Krbiľa J., Kříž F.: Transformácia binomických lineárnych diferencialnych rovníc n-tého rádu, ktorých nosiče sú komplexné funkcie reálného argumentu. Práce a štúdie VŠD v Žiline, No 1, 1974, séria mat.-fyz., 77-82. MR 0397062

[10] Staněk S.: On a structure of the intersection of the set of dispersions of two second-order linear differential equations. Acta Univ.Palac.Olomucensis, Fac. rer. nat., vol 73, 1982, 79-85. MR 0702610 | Zbl 0543.34026

[11] Staněk S.: On the intersection of the set of solutions of two Kummer's differential equations. Acta Univ. Palac. Olomucensis, Fac. rer. nat., vol. 79, 1984, 25-32. MR 0837026 | Zbl 0596.34014

[12] Staněk S.: On the intersection of groups of increasing dispersions of two second order oscillatory differential equations. Acta Univ. Palac. Olomucensis, Fac. rer. nat., vol. 86, Math. XXIV, 1985. 61-66. MR 0879022

[13] Staněk S.: Introducing A phase of the differential equation y'' = Q(t)y with a complex coefficient Q of a real variable. Acta Univ. Palac. Olomucensis, vol. 85, Math. XXIV, 1986, 57-75. MR 0918369

[14] Wilczynski E. J.: Projective differential geometry of curves and ruled surfaces. Leipzig, 1906.