It is convenient to start with a situation in which the NS enters a binary system with a normal star losing matter in the form of a stellar wind. Numerical simulation of the evolution of NS shows (Lipunov and Prokhorov, 1987[115]) that the fraction of ejecting stars in massive systems with normal components may be as high as several tens of percent of the total number of binary systems (see Figure 27). Below we describe some sources with appropriate properties.