Fritsch, Rudolf Variations on the theorems of Jordan-Hölder and Schreier. (English) Zbl 0244.18002 J. Pure Appl. Algebra 2, 209-229 (1972). MSC: 18A20 × Cite Format Result Cite Review PDF Full Text: DOI Link
Fritsch, Rudolf; Wyler, Oswald The Schreier refinement theorem for categories. (English) Zbl 0257.18010 Arch. Math. 22, 570-572 (1971). MSC: 18A30 20N99 20E15 × Cite Format Result Cite Review PDF Full Text: DOI