“…There are plenty of phenomena where the presence of delays is to necessarily considered [3,4,5,6,7]. Equation of the form (1.1) has been studied extensively in the case where r 3 = r 4 = 0 (see,e.g., [8,9,10,11,12,13]. The accessibility of exact solutions as well as efficient methods to obtain numerical approximations of required precision are very important.…”