On distribution of the roots for an exponential polynomial equation with applications (Q1726578)

The paper studies a special case of Liénard neutral differential equations in the form \[ (x(t)+px(t-\tau))''+f(x(t))x'(t)+g(x(t-\tau))=0. \] By studying the distribution of roots of the characteristic equation, the authors try to find the answer to the question how the parameter $p$ affects the stability of the zero solution. Furthermore, they find the value of $p$ in which Hopf bifurcation at the origin occurs.