Angelova , Gergana, Petar Parvanov, Georgi chetrafilov, Nadezhda Krasteva, y Vladislav Krastev. 2017. «SUSTAINABILITY IN TOURISM CADRE TRAINING AND SELECTION IN BULGARIA». Revista Inclusiones, junio, 144-56. https://www.revistainclusiones.org/index.php/inclu/article/view/583.