A method for preparation of multi-layer polymeric microspheres formed from any degradable or non-degradable polymers which are not soluble in each other at a particular concentration, but which have a positive spreading coefficient in solution. The multi-layer microspheres produced by the method are...http://www.google.fr/patents/US5912017?utm_source=gb-gplus-shareBrevet US5912017 - Multiwall polymeric microspheres
