Mendes, E., P. E. M. Carvalho, and L. M. Ferreira Gomes. “Hydrogeologic Framework of the Gardunha Mountain: Northeast Area – Central Portugal”. Communications - Scientific Letters of the University of Zilina, Vol. 12, no. 3A, Oct. 2010, pp. 98-103, http://journals.uniza.sk/index.php/communications/article/view/953.