ŞUBĂ, A., and S. TURUTA. “CUBIC DIFFERENTIAL SYSTEMS WITH A WEAK FOCUS AND A REAL INVARIANT STRAIGHT LINE OF MAXIMAL ALGEBRAIC MULTIPLICITY ”. Acta Et Commentationes Exact and Natural Sciences, Vol. 4, no. 2, July 2019, pp. 119-30, doi:10.36120/2587-3644.v4i2.119-130.