Centers of projective vector fields of spatial quasi-homogeneous systems with weight <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo form="prefix">(</mml:mo> <mml:mi>m</mml:mi> <mml:mo>,</mml:mo> <mml:mi>m</mml:mi> <mml:mo>,</mml:mo> <mml:mi>n</mml:mi> <mml:mo form="postfix">)</mml:mo> </mml:mrow> </mml:math> and degree <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:math> on the sphere
Electronic journal on the qualitative theory of differential equations