Voldman M., Vulpe Nicolae
Affine invariant coefficient conditions for quadratic system to possess two conjugate imaginary straight line solutions as well as two couples of such lines as solutions are established. For some classes of quadratic systems with two imaginary invariant straight lines the necessary and sufficient affine invariant conditions for possessing just one limit cycle are determined.
Academy of Science of Moldova
Institute of Mathematics and Computer Science
Academiei str. 5, MD-2028 Chisinau, Moldova
Whitehead College, University of Redlands
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