The four known biplanes with<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="$k = 11$"><mml:mrow><mml:mi>k</mml:mi><mml:mo>=</mml:mo><mml:mn>11</mml:mn></mml:mrow></mml:math>
International Journal of Mathematics and Mathematical Sciences