Star complexes and starburst clumps in spiral galaxies
  Star complexes are the highest level groupings in the hierarchy of the embedded young stars, clusters and associations, which obey the size - age relation. Starburst clumps, superassociations, supergiant HII regions are different titles for the groupings of the same size as complexes but with active star formation over all the grouping. The coherent star formation in the regions of violent star formation was probably triggered by external pressure. The issue of gravitational boundness of complexes and superassociations is briefly discussed 
Yu.N.Efremov