Complex sentence: In 1967, the territory of Saint Christopher-Nevis-Anguilla was granted full internal autonomy and in 1971, the island of Anguilla rigorously sought and achieved becoming separate, in 1980 the seperation from the Federation of Saint Kitts and Nevis became formally accepted.
Split into simpler sentences: In 1967, the territory of Saint Christopher-Nevis-Anguilla was granted full internal autonomy. In 1971, the island of Anguilla rigorously sought and achieved becoming separate; in 1980, the seperation from the Federation of Saint Kitts and Nevis became formally accepted.