On the existence of positive periodic solutions for neutral functional differential equation with multiple deviating arguments (Q1879150)

By means of an abstract continuation theory for \(k\)-set contraction and a continuation theorem of the coincidence degree principle, some criteria are established for the existence of positive periodic solutions of the following neutral functional-differential equation \[ \frac{dN}{dt}=N(t)[a(t)-\beta(t)N(t)-\sum\limits_{j=1}^{n}b_j(t)N(t-\sigma_j(t)) -\sum\limits_{i=1}^{m}c_i(t)N'(t-\tau_i(t))]. \]