of Morocco to cross the border in a peaceful march. A few days before, on 31 October, Moroccan troops invaded Western Sahara from the north. Demands for independence In the waning days of General Franco's rule, and after the Green March, the Spanish government signed a tripartite agreement with Morocco and Mauritania as it moved to transfer the territory on 14 November 1975. The accords were based on a bipartite administration, and Morocco and Mauritania each moved to annex the territories, with Morocco taking control of the northern two-thirds of Western Sahara as its Southern Provinces, and Mauritania taking control of the southern third as Tiris al-Gharbiyya. Spain terminated its presence in Spanish Sahara within three months, repatriating Spanish remains from its cemeteries. The Moroccan and Mauritanian annexations were resisted by the Polisario Front, which had gained backing from Algeria. It initiated guerrilla warfare and, in 1979, Mauritania withdrew due to pressure from Polisario, including a bombardment of its capital and other economic targets. Morocco extended its control to the rest of the territory. It gradually contained the guerrillas by setting up the extensive sand-berm in the desert (known as the Border Wall or Moroccan Wall) to exclude guerrilla fighters. Hostilities ceased in a 1991 cease-fire, overseen by the peacekeeping mission MINURSO, under the terms of a UN Settlement Plan. Stalling of the referendum and Settlement Plan The referendum, originally scheduled for 1992, foresaw giving the local population the option between independence or affirming integration with Morocco, but it quickly stalled. In 1997, the Houston Agreement attempted to revive the proposal for a referendum but likewise has hitherto not had success. , negotiations over terms have not resulted in any substantive action. At the heart of the dispute lies the question of who qualifies to be registered to participate in the referendum, and, since about the year 2000, Morocco considers that since there is no agreement on persons entitled to vote, a referendum is not possible. Meanwhile, Polisario still insisted on a referendum with independence as a clear option, without offering a solution to the problem of who is qualified to be registered to participate in it. Both sides blame each other for the stalling of the referendum. The Polisario has insisted on only allowing those found on the 1974 Spanish Census lists (see below) to vote, while Morocco has insisted that the census was flawed by evasion and sought