Let $A$ and $B$ two events such that $P\left( {\overline {A \cup B} } \right) = {1 \over 6},$ $P\left( {A \cap B} \right) = {1 \over 4}$ and $P\left( {\overline A } \right) = {1 \over 4},$ where ${\overline A }$ stands for complement of event $A$. Then events $A$ and $B$ are :