The series Lectures Notes in Computer Science and Technologies of the Institute of Information and Communication Technologies at the Bulgarian Academy of Sciences presents in an electronic format textbooks for undergraduate, graduate and PhD students studied various programs related to Informatics, Computational Mathematics, Mathematical Modeling, Communication Technologies, etc., as well as for all readers interested in these scientific disciplines. The Lecture Notes are based on courses taught by scientists of the Institute of Information and Communication Technologies - BAS in various Bulgarian universities and the Center for Doctoral Training in BAS. The published materials are with open access - they are freely available without any charge.