Abstract:
In the present article, we continue to study the complexity of the lattice of quasivarieties of graphs. For every quasivariety $\mathbf{K}$ of graphs that contains a non-bipartite graph, we find a subquasivariety $\mathbf{K}^\prime\subseteq\mathbf{K}$ such that there exist $2^\omega$ subquasivarieties $\mathbf{K}^{\prime\prime}\in\mathrm{L_q}(\mathbf{K}^\prime)$ without covers (hence, without independent bases for their quasi-identities in $\mathbf{K}^\prime$).
Key words:quasivariety, graph, basis for quasi-identities.