Georgiev, D. , Bogdanov, B. , Markovska, I. , Hristov, Y. , Stanev, D.. "A Kinetic Study on the Adsorption of Cd(II) and Zn(II) Ions from Aqueous Solutions on Zeolite NaA". World Academy of Science, Engineering and Technology, Open Science Index 59, International Journal of Materials and Metallurgical Engineering (2011), 5(11), 1003 - 1006.