Obviously, the question on a turn-out/approval quorum applies only to those countries where such a quorum is provided for.  The 50% turn-out threshold was not achieved in 18 out of 53 abrogative referendums in Italy, in two out of six in Lithuania, in one out of two in “the former Yugoslav Republic of Macedonia” and in Portugal.  In this latter case, the effect of the referendum was then merely consultative. With regard to approval quorums, the only referendum held in Armenia since the adoption of the current constitution failed as it was not approved by a third of the electorate.  Similarly, one referendum (out of the four that have been held) in Hungary was invalidated as none of the alternatives in the question obtained the approval of one quarter of the electorate.