 At the same time, the energy-based U.S. trading relationship continues to expand and spark other ties.One offshoot has been the development of a Sister City relationship between Lafayette, Louisiana and Cabinda and between Houston, Texas and Luanda.The Catholic University of Luanda has close links with a number of American institutions and has received support from the Angola Educational Assistance Fund, a U.S. non-profit organization organized by Citizens Energy of Boston.