In September 2014 we accepted the proposal sent by Prof. Xiao-Jun Yang (Department of Mathematics and Mechanics, China University of Mining and Technology, Xuzhou, Jiangsu), Prof. Dumitru Baleanu (Department of Mathematics and Computer Sciences, Faculty of Art and Sciences, Cankaya University, Ankara), and Prof. Gongnan Xie (School of Mechanical Engineering, Northwestern Polytechnical University, Xi'an, Shaanxi, China), to prepare jointly the special issue of the journal Thermal Science, dedicated to the NON- -LINEAR DIFFUSION MODELS IN HEAT AND MASS TRANSFER, containing a special collection of articles devoted to the 60th birthday of Prof. Jordan Hristov. National Editorial Board of the journal Thermal Science accepted this proposal with great pleasure, having in mind the great research contribution of Prof. Jordan Hristov, not only in the fields of the heat and mass transfer but also in developing the quality of our journal. My pleasure was even greater since with Prof. Hristov I had many discussions in the past, and he approved himself as a sincere friend of our journal and a reliable friend of me.