“…(It is known that neglecting the dislocation-dislocation correlations leads to unphysical results [8,9].) It is found that correlation effects enter into the theories through gradientlike stress terms [6,8,14], which were already proposed earlier phenomenologically [15,16]. Motivated by its crucial role many investigations on the properties of dislocation correlations have been published recently [17,18,19,20,21].…”