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Bibliography

[1]

S. A. Amitsur, Commuting linear differential operators, Pacific J. Math. 8 (1959), 1-10. MR 0095305 (20:1808)

[2]

G. Birkhoff, Lattice theory, Amer. Math. Soc. Colloq. Publ., Vol. 25, Amer. Math. Soc., Providence, R. I., 1948. MR 0029876 (10:673a)

[3]

N. Bourbaki, Eléments de mathématique. Fasc. XXVI: Groupes et algèbres de Lie, Chapitre 1, Algèbres de Lie, Hermann, Paris, 1960.

[4]

P. M. Cohn, On subsemigroups of free semigroups, Proc. Amer. Math. Soc. 13 (1962), 347-351. MR 0139680 (25:3111)

[5]

P. M. Cohn, On a generalization of the Euclidean algorithm, Proc. Cambridge Philos. Soc. 57 (1961), 18-30. MR 0118743 (22:9514)

[6]

-, Factorization in noncommuting power series rings, Proc. Cambridge Philos. Soc. 58 (1962), 452-464. MR 0138649 (25:2092)

[7]

-, Noncommutative unique factorization domains, Trans. Amer. Math. Soc. 109 (1963), 313-331. MR 0155851 (27:5785)

[8]

-, Rings with weak algorithm, Trans. Amer. Math. Soc. 109 (1963), 332-356. MR 0153696 (27:3657)

[9]

-, Subalgebras of free associative algebras, Proc. London Math. Soc. (3) 14 (1964), 618-632. MR 0167504 (29:4777)

[10]

-, Free ideal rings, J. Algebra 1 (1964), 47-69. MR 0161891 (28:5095)

[11]

-, Some remarks on the invariant basis property, Topology 5 (1966), 215-228. MR 0197511 (33:5676)

[12]

P. M. Cohn and G. M. Bergman, Dependence in rings. I: n-firs, (to appear).

[13]

P. M. Cohn, Dependence in rings. II: The dependence number, (to appear). MR 0279122 (43:4848)

[14]

H. Flanders, Commuting linear differential operators, Tech. Rep. No. 1, Univ of California, Berkeley, 1955, 39 pp.

[15]

B. V. Tarasov, O svobodnyh associativnyh algebrah, Algebra i Logika Sem. 6 (1967), 93-105.

[16]

O. Zariski and P. Samuel, Commutative algebra, Van Nostrand, Princeton, N. J., 1958. MR 0090581 (19:833e)

[17]

G. M. Bergman, Ranks of tensors and base extension, J. Algebra (to appear) MR 0242850 (39:4177)