Issues in relation to which referendums are mandatory at the national level

Austria
Answer
Constitutional amendments
Source
B-VG Art. 44 (3)
http://www.ris.bka.gv.at/GeltendeFassung.wxe?Abfrage=Bundesnormen&Gesetzesnummer=10000138
Comment
Areferendum is only mandatory if the National Council decided upon a totalrevision of the Federal Constitutional Law.