LIBREVILLE, Sept. 4 (Xinhua) -- Brice Oligui Nguema, president of the Committee for the Transition and Restoration of Institutions (CTRI), was sworn in as Gabon's "transitional president" in the capital of Libreville Monday, promising the adoption of a new constitution by referendum and "fair" elections after the transition. The swearing-in ceremony was held at the presidential palace, known as the "Renovation Palace." "I solemnly and honorably undertake to do everything possible to achieve