Finding a systematic construction for integrable partial differential
systems in four independent variables is a long-standing problem in modern
theory of integrable systems. In this talk we address the problem in
question by presenting a broad new class of (3+1)-dimensional dispersionless
integrable systems possessing nonisospectral Lax pairs written in terms of
contact vector fields;  please see arXiv:1401.2122 (to appear in Lett. Math.
Phys. (2017)) for details.