Process for making retroreflector sheet having protrusions which are retroreflective on selected side surfaces of the protrusions. Continuous web of polymeric base sheet having a front surface with a plurality, of protrusions, each protrusion having a top surface and at least one side surface, is provided....http://www.google.co.uk/patents/US4988541?utm_source=gb-gplus-sharePatent US4988541 - Process for making retroreflector sheet
