Author,Title,Journal,ISSN,Publisher,Date,Volume,Number,Page,URL,URL(DOI) Kumpera A,On the Lie and Cartan Theory of Invariant Differential Systems,"Journal of mathematical sciences, the University of Tokyo",13405705,The University of Tokyo,1999,6,2,229-314,https://cir.nii.ac.jp/crid/1570854176776977280,