1. F. Aicardi and L. G. Fel, Gaps in nonsymmetric numerical semigroups, Israel Journal of Mathematics 175 (2010), 85–112.
2. V. Barucci and R. Fröberg, One-dimensional almost Gorenstein rings, Journal of Algebra 188 (1997), 418–442.
3. D. Eisenbud, The Geometry of Syzygies. A 2nd Course in Commutative Algebra and Algebraic Geometry, Springer-Verlag, New York, 2005.
4. L. G. Fel, Frobenius problem for semigroups S(d1, d2, d3), Functional Analysis and Other Mathematics 1 (2006), 119–157.
5. I. M. Gessel and R. P. Stanley, Algebraic enumeration, in Handbook of Combinatorics, Vol. 2 (R. L. Graham, M. Grötschel and L. Lovász eds.), Elsevier, Amsterdam, 1995, pp. 1036–1039.