• The period function in a class of quadratic kolmogoroff systems. 

    Uribe, Marco; Wallace, Myrna (2000)
    In this paper we consider the family of quadratic Kolmogoroff systems with a center in the real quadrant: (:x=x(1ÄxÄay):y=y(Ä1 +ax+y), where 1< a <1: This system has three invariant lines (the coordinate axes and the line ...