@book{401380, title = {Linear Differential Transformations of the Second Order}, series = {GDML\_Books}, publisher = {The English Universities Press, Ltd.}, address = {London}, year = {1971}, mrnumber = {MR0463539}, zbl = {0222.34002}, language = {en}, url = {http://dml.mathdoc.fr/item/401380} }
Borůvka, Otakar. Linear Differential Transformations of the Second Order. GDML_Books (1971), http://gdmltest.u-ga.fr/item/401380/