[1] G. H. BERGMAN: Functors from finite sets to finite sets. - preprint.

[2] P. FREYD: Abelian Categories. New York, 1964. Zbl 0121.02103

[3] P. FREYD: On the concreteness of certain categories. - preprint. MR 0322006 | Zbl 0248.18008

[4] V. KOUBEK: Set functors. Comment. Math. Univ. Carolinae 12 (1971), 175-195. MR 0286860 | Zbl 0217.06803

[5] V. TRNKOVÁ: On descriptive classification of set functors, I, II. Comment. Math. Univ. Carolinae 12 (1971), 143-175 (Part I), 345-357 (Part II). MR 0294445

[6] V. TRNKOVÁ: Some properties of set functors. Comment. Math. Univ. Carolinae 10 (1969), 323-352. MR 0252474

[7] A. TARSKI: Sur la décomposition des ensembles en sousensembles prèsque disjoints. Fund. Math. 14 (1929), 205-215.