Added single ticks around polynomial expression
Added single ticks around polynomial expression

bashtage/statsmodels,statsmodels/statsmodels,bashtage/statsmodels,bashtage/statsmodels,josef-pkt/statsmodels,josef-pkt/statsmodels,statsmodels/statsmodels,statsmodels/statsmodels,bashtage/statsmodels,bashtage/statsmodels,josef-pkt/statsmodels,statsmodels/statsmodels,josef-pkt/statsmodels,bashtage/statsmodels,statsmodels/statsmodels,statsmodels/statsmodels,josef-pkt/statsmodels,josef-pkt/statsmodels