think it will be present Slovenia. Czechoslovakia was often confused with it.
you are right, also castlegarden has nothing about them.....
slovenian phonebook has in any case for Slak 13 hits at business(PODJETJA) and 202(OSEBE) hits at peoplepages.
write in lastname at Kdo • Kaj? and click on NAJDI.
for Gregoric 51 hits at business and 469 at peoplepages.http://www.itis.si/
phonebook-results for present Austria.http://www.herold.at/en/telefonbuch/
5 Slak in following states:
Burgenland (1) http://www.herold.at/telefonbuch/slak/
55 Gregoric in following states:
Vorarlberg (1) http://www.herold.at/telefonbuch/gregoric/