Another amendment to the constitution was adopted on 4 September 1992 and went into effect on 25 September 1992. Modeled after the Constitution of Portugal, the new amendment entrenched the ideas of political pluralism and a balance of powers in government,[7] creating a multi-party system.[8] This was further expanded upon by an amendment in 1999, which specifically defined the nation as "a sovereign, unitary and democratic republic, which guarantees respect for human dignity and recognises the inviolability and inalienability of human rights as the foundation of the entire human community, of peace and of justice".[1][9] The constitution was last amended in 2010.[2]