@article {IOPORT.06083824,
    author       = {Omanadze, R.Sh. and Chitaia, I.O.},
    title        = {$Q _{1}$-degrees of c.e. sets.},
    year         = {2012},
    journal      = {Archive for Mathematical Logic},
    volume       = {51},
    number       = {5-6},
    issn         = {0933-5846},
    pages        = {503-515},
    publisher    = {Springer-Verlag, Berlin},
    doi          = {10.1007/s00153-012-0278-7},
    abstract     = {Summary: We show that the $Q$-degree of a hyperhypersimple set includes an infinite collection of $Q _{1}$-degrees linearly ordered under ${\leq_{Q_1}}$ with order type of the integers and consisting entirely of hyperhypersimple sets. Also, we prove that the c.e. $Q _{1}$-degrees are not an upper semilattice. The main result of this paper is that the $Q _{1}$-degree of a hemimaximal set contains only one c.e. 1-degree. Analogous results are valid for $\Pi_1^0s_1$-degrees.},
    identifier   = {06083824},
}