What forms of checks are undertaken to verify signatures?

Law 8492 Referendum regulations (Decreto 8492 para laRegulaci?n del refer?ndum) art  9;

http://?aceproject.?org/?ero-?en/?regions/?americas/?CR/?costa-?rica-?decreto-?8492-?para-?la-?regulacion-?del

Law 8491 Citizens? Initiative (Ley 8491 de IniciativaPopular) art. 3. 
http://?aceproject.?org/?ero-?en/?regions/?americas/?CR/?costa-?rica-?ley-?8491-?de-?iniciativa-?popular-?2012