id: 05778937
dt: j
an: 05778937
au: Almeida, Jorge; Klíma, Ondřej
ti: A counterexample to a conjecture concerning concatenation hierarchies.
so: Inf. Process. Lett. 110, No. 1, 4-7 (2009).
py: 2009
pu: Elsevier Sciences Publishers (North-Holland), Amsterdam
la: EN
cc: 
ut: formal languages; regular languages; concatenation hierarchies; level two;
    star-free languages
ci: 
li: doi:10.1016/j.ipl.2009.09.011
ab: Summary: We give a counterexample to the conjecture which was originally
    formulated by Straubing in 1986 concerning a certain algebraic
    characterization of regular languages of level 2 in the
    Straubing-Thérien concatenation hierarchy of star-free languages.
rv: