 \rat \mole \horse\chicken ( | { \bf p } | - { \bf p } \cdot { \bf \sigma } ) \left ( \begin {array} { c } \phi ( \tilde { z } , \bar { \tilde { z } } , | { \bf p } | ) \\ \phi ( z , \bar { z } , | { \bf p } | ) \end {array} \right ) = 0