Using unavoidable set of trees to generalize Kruskal's theorem
Journal of Symbolic Computation
Well quasi-orders and regular languages
Acta Informatica
On quasi orders of words and the confluence property
Theoretical Computer Science
On well quasi orders of free monoids
Theoretical Computer Science - Special issue: papers dedicated to the memory of Marcel-Paul Schützenberger
Shuffle and scattered deletion closure of languages
Theoretical Computer Science
Finiteness and Regularity in Semigroups and Formal Languages
Finiteness and Regularity in Semigroups and Formal Languages
Well quasi-orders and context-free grammars
Theoretical Computer Science - Developments in language theory
On well quasi-orders on languages
DLT'03 Proceedings of the 7th international conference on Developments in language theory
Well Quasi-orders in Formal Language Theory
DLT '08 Proceedings of the 12th international conference on Developments in Language Theory
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Given a set I of words, the set L$_{\rm \vdash}^{\epsilon}~_{\rm I}$ of all words obtained by the shuffle of (copies of) words of I is naturally provided with a partial order: for u, v in L$_{\rm \vdash}^{\epsilon}~_{\rm I}$, u$\vdash^{\rm *}_{I}$v if and only if v is the shuffle of u and another word of L$_{\rm \vdash}^{\epsilon}~_{\rm I}$. In [3], the authors have stated the problem of the characterization of the finite sets I such that $\vdash_{I}^{\rm *}$ is a well quasi-order on L$_{\rm \vdash}^{\epsilon}~_{\rm I}$. In this paper we give the answer in the case when I consists of a single word w.