Complex sentence: The referendum was officially announced in December and was planned to be held on 10--16 May 2010 with two projects to be chosen and an option to dismiss them by voting using touchscreens installed in several municipal offices used as polling places or through the Internet.
Split into simpler sentences: The referendum was officially announced in December and was planned to be held on 10--16 May 2010 with two projects to be chosen and an option to dismiss them. The voting process would take place at several municipal offices used as polling places by voting using touchscreens, though it was also possible to vote through the Internet.