Compatible relations on filters and stability of local topological   properties under supremum and product
  An abstract scheme using particular types of relations on filters leads to general unifying results on stability under supremum and product of local topological properties. We present applications for Frechetness, strong Frechetness, countable tightness and countable fan-tightness, some of which recover or refine classical results, some of which are new. The reader may find other applications as well. 
Francis Jordan, Frederic Mynard