<P> Under the current Constitution of Bulgaria (1991), there are two procedures for amendment, depending on the part of the constitution to be amended: </P> <Ul> <Li> Normal amendment procedure (Articles 153--156): the Parliament can amend the Constitution for minor issues with a two - thirds majority . This shall be done in three successive readings . </Li> <Li> Special amendment procedure (Articles 157--163): this procedure is the only way to revise the international borders of Bulgaria; change the form of government in the country; change the form in which the Constitution and international treaties are applied in Bulgaria (Article 5) or suspend citizens' rights . When such amendment is needed, the Constitution envisages an election for Great National Assembly, which consists of 400 deputies, with 200 elected by proportional vote and 200 elected by the first - past - the - post method . Then the amendments to the Constitution are passed by two - thirds majority in three successive readings . </Li> </Ul> <Li> Normal amendment procedure (Articles 153--156): the Parliament can amend the Constitution for minor issues with a two - thirds majority . This shall be done in three successive readings . </Li> <Li> Special amendment procedure (Articles 157--163): this procedure is the only way to revise the international borders of Bulgaria; change the form of government in the country; change the form in which the Constitution and international treaties are applied in Bulgaria (Article 5) or suspend citizens' rights . When such amendment is needed, the Constitution envisages an election for Great National Assembly, which consists of 400 deputies, with 200 elected by proportional vote and 200 elected by the first - past - the - post method . Then the amendments to the Constitution are passed by two - thirds majority in three successive readings . </Li>

What proposal in modified form became the basis for the constitution