A Slovak referendum on a constitutional amendment has been declared invalid due to the low turnout, with fewer than 50% of those eligible to vote, the minimum needed, coming to cast their ballot. Only 27.25% of voters took part, rendering the election invalid, the state election commission said on Sunday. Of those who did vote, some 97.5% were in favour of the constitutional amendment. This will not have any formal effect, however. The supporters of the constitutional amendment wanted to allow early elections in Slovakia, as is common in other EU countries. Until now, the Slovakian constitutio…