sentences:  Other frequently encountered structures comprise pulse trains (also known as periodic travelling waves), spiral waves and target patterns.These three solution types are also generic features of two- (or more-) component reaction–diffusion equations in which the local dynamics have a stable limit cycle
  
  For a variety of systems, reaction–diffusion equations with more than two components have been proposed, e.g.as models for the regulation of lymphangiogenesis by VEGFC, MMP2, and collagen I; the Belousov–Zhabotinsky reaction, for blood clotting or planar gas discharge systems.