1. Periodic solutions of a quartic non-autonomous equation;Alwash;Nonlinear Analysis,1987
2. Groebner bases: an algorithmic method in polynomial ideal theory;Buchberger,1985
3. On the number of solutions of the equations dx/dt=∑j=0naj(t)tj,0≤t≤1, for which x(0) = x(1);Lins Neto;Inv. Math.,1980
4. The number of periodic solutions of the equation z˙=zN+p1(t)zN−1+⋯+pN(t);Lloyd,1973
5. Periodic solutions of polynomial first order differential equations;Shahshahani;Nonlinear Analysis,1981