Complex sentence: These negotiations were completed by the end of the year, the new treaty which had previously been referred to as the "Reform Treaty" become the Lisbon Treaty on its signing in Lisbon on 13 December 2007.
Split into simpler sentences: These negotiations were completed by the end of the year. The new treaty, which had previously been referred to as the "Reform Treaty", became the Lisbon Treaty on its signing in Lisbon on 13 December 2007.