Y. Fuh and P. Mishra, Type inference with subtypes, Theoretical Computer Science, vol.73, issue.2, pp.155-175, 1990.
DOI : 10.1016/0304-3975(90)90144-7
URL : http://doi.org/10.1016/0304-3975(90)90144-7

J. C. Mitchell, Abstract, Journal of Functional Programming, vol.17, issue.03, pp.245-285, 1991.
DOI : 10.1016/S0019-9958(82)80087-9

R. M. Amadio and L. Cardelli, Subtyping recursive types, ACM Transactions on Programming Languages and Systems, vol.15, issue.4, pp.575-631, 1993.
DOI : 10.1145/155183.155231
URL : https://hal.archives-ouvertes.fr/inria-00070035

J. Eifrig, S. Smith, and . Trifonov, Sound polymorphic type inference for objects, ACM Conference on Object-Oriented Programming: Systems, Languages, and Applications, pp.169-184, 1995.

F. Pottier, Simplifying subtyping constraints, ACM SIGPLAN International Conference on Functional Programming, pp.122-133, 1996.
DOI : 10.1145/232627.232642
URL : http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.41.7032

F. Pottier, Type inference in the presence of subtyping: from theory to practice, 1998.
URL : https://hal.archives-ouvertes.fr/inria-00073205

D. Kozen, J. Palsberg, and M. I. Schwartzbach, Efficient inference of partial types, Journal of Computer and System Sciences, vol.49, issue.2, pp.306-324, 1994.
DOI : 10.1016/S0022-0000(05)80051-0

J. Palsberg, M. Wand, and P. O. Keefe, Type inference with non-structural subtyping, Formal Aspects of Computing, vol.5, issue.3, pp.49-67, 1997.
DOI : 10.1007/BF01212524
URL : http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.16.3123

D. Kozen, J. Palsberg, and M. I. Schwartzbach, Efficient recursive subtyping, Mathematical Structures in Computer Science, vol.5, pp.1-13, 1995.
DOI : 10.7146/dpb.v21i405.6639
URL : http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.127.3594

J. Eifrig, S. Smith, and . Trifonov, Type inference for recursively constrained types and its application to object-oriented programming, Electronic Notes in Theoretical Computer Science, vol.1

J. Rehof, Minimal typings in atomic subtyping, Proceedings of the 24th ACM SIGPLAN-SIGACT symposium on Principles of programming languages , POPL '97, pp.278-291, 1997.
DOI : 10.1145/263699.263738

F. Pottier, A framework for type inference with subtyping, ACM SIGPLAN International Conference on Functional Programming, pp.228-238, 1998.

J. Rehof, The complexity of simple subtyping systems, 1998.

F. Henglein and J. Rehof, The complexity of subtype entailment for simple types, Proceedings of Twelfth Annual IEEE Symposium on Logic in Computer Science, pp.362-372, 1997.
DOI : 10.1109/LICS.1997.614961

F. Henglein and J. Rehof, Constraint automata and the complexity of recursive subtype entailment, International Colloquium on Automata, Languages, & Programming, pp.616-627, 1998.
DOI : 10.1007/BFb0055089

J. Niehren and T. Priesnitz, Entailment of Non-structural Subtype Constraints, Lecture Notes in Computer Science, vol.1742, pp.251-265, 1999.
DOI : 10.1007/3-540-46674-6_22
URL : https://hal.archives-ouvertes.fr/inria-00536825

G. Makanin, THE PROBLEM OF SOLVABILITY OF EQUATIONS IN A FREE SEMIGROUP, Mathematics of the USSR-Sbornik, vol.32, issue.2
DOI : 10.1070/SM1977v032n02ABEH002376

W. Plandowski, Satisfiability of word equations with constants is in PSPACE, IEEE Symposium on Foundations of Computer Science, pp.495-500, 1999.

M. Müller, J. Niehren, and R. Treinen, The first-order theory of ordering constraints over feature trees, IEEE Symposium on Logic in Computer Science, pp.432-443, 1998.

J. Niehren, M. Müller, and J. Talbot, Entailment of atomic set constraints is PSPACE-complete, Proceedings. 14th Symposium on Logic in Computer Science (Cat. No. PR00158), pp.285-294, 1999.
DOI : 10.1109/LICS.1999.782623
URL : https://hal.archives-ouvertes.fr/inria-00536817

Z. Su, A. Aiken, J. Niehren, T. Priesnitz, and R. Treinen, First-order theory of subtyping constraints, ACM SIGPLAN-SIGACT Symposium on Principles of Programming Languages, pp.203-216, 2002.
URL : https://hal.archives-ouvertes.fr/inria-00536828

R. Treinen, Predicate Logic and Tree Automata with Tests, Lecture Notes in Computer Science, vol.1784, pp.329-343, 2000.
DOI : 10.1007/3-540-46432-8_22
URL : http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.31.9969

J. Niehren and T. Priesnitz, Non-structural Subtype Entailment in Automata Theory, Fourth International Symposium on Theoretical Aspects of Computer Software, pp.360-384, 2001.
DOI : 10.1007/3-540-45500-0_18
URL : https://hal.archives-ouvertes.fr/inria-00536514

K. U. Schulz, Makanin's algorithm for word equations-two improvements and a generalization, Word Equations and Related Topics, pp.85-150, 1991.
DOI : 10.1007/3-540-55124-7_4

V. Durnev, Unsolvability of positive ?? 3 -theory of free groups, in: Sibirsky mathematichesky jurnal, Russian, also exists in English translation, pp.1067-1080, 1995.

F. Baader and K. Schulz, Unification in the Union of Disjoint Equational Theories: Combining Decision Procedures, Journal of Symbolic Computation, vol.21, issue.2, pp.211-243, 1996.
DOI : 10.1006/jsco.1996.0009

Y. Vazhenin and B. Rozenblat, Decidability of the positive theory of a free countably generated semigroup, Mathematics of the USSR Sbornik, pp.109-116, 1983.

J. Palsberg and P. O. Keefe, A type system equivalent to flow analysis, ACM Transactions on Programming Languages and Systems, vol.17, issue.4, pp.576-599, 1995.
DOI : 10.1145/210184.210187