Model Checking Positive Equality-free FO: Boolean Structures and Digraphs of Size Three

Barnaby Martin Model Checking Positive Equality-free FO: Boolean Structures and Digraphs of Size Three http://arxiv.org/abs/0808.0647 2008 CoRR abs/0808.0647 db/journals/corr/corr0808.html#abs-0808-0647 informal publication