I. Anderson: Perfect matchings of a graph.
J. Comb. Theory B 10 (1971), 183-186.

Philipp Hall: On representatives of subsets.
J. London MS 10 (1935), 26-30.

Denes Ko''nig: Graphen und Matrisen.
Mat. Fiz. Lapok 38 (1931), 116-119.

L. Lovasz/M. Plummer: Matching theory. North-Holland 1986.

P. Maschlanka/Lutz Volkmann: Independence number in n-extendable
graphs. Discrete Math. ... (ca. 1995), ...

M. Plummer: On n-extendable graphs.
Discrete Math. 31 (1980), 201-210.

M. Plummer: Extending matchings in graphs. A survey.
Discrete Math. 127 (1994), 277-292.

Q. Yu: A note on n-extendable graphs.
J. Graph Theory 16 (1992), 349-353.

Q. Yu: Characterizations of various matching extensions graphs.
Australas. J. Comb. 7 (1993), 55-64.