New singular defect-like solutions of the 2-dimensional elliptic sine-Gordon equation were found by using the inverse scaling transform. The non-linear defects were similar, in their topological properties, to those found in the linear theory of elasticity, and included dislocations, disclination dipoles, point defects and twins.

New Nonlinear Defects in 2D Crystals. V.V.Kiseliev: Physics Letters A, 1998, 244[1-3], 103-10