Solitary waves in a two-parameter family of generalized nonlinear Dirac equations in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si25.svg" display="inline" id="d1e718"> <mml:mrow> <mml:mn>1</mml:mn> <mml:mo linebreak="goodbreak" linebreakstyle="after">+</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:math> dimensions