What forms of checks are undertaken to verify signatures?

Law of Ukraine onall-Ukrainian and Local Referendums

http://www.legislationline.org/documents/action/popup/id/7114

ARTICLE19.  Duringthe collection of signatures, the Chairperson of an appropriate Council ofpeoples' deputies, where signatures of the initiative group members arecertified, shall organize the checking of the authenticity of records onpetition forms. In case of violations of signature collecting procedures andpetition forms execution are revealed, the Chairperson of rayon, city (citiesof republican and oblast subordination) Councils of people deputies, in theterritory which the all-Ukrainian referendum initiative group carries out itsactivity, shall submit a presentation to the Central Commission on all-Ukrainianreferendum.