University of KashanMathematics Interdisciplinary Research2538-36394220191201Mathematical Chemistry Works of Dragos Cvetkovic1291369550710.22052/mir.2019.204819.1168ENIvan GutmanFaculty of Science, University of Kragujevac, Kragujevac, SerbiaJournal Article20191006In addition to his countless contributions to spectral graph theory, some works of Dragos Cvetkovic are concerned with chemical problems. These are briefly outlined, with emphasis on his collaboration with the present author.http://mir.kashanu.ac.ir/article_95507_a3c70aacf4be9f0debdcebff4ab63c45.pdfUniversity of KashanMathematics Interdisciplinary Research2538-36394220191201Seidel Integral Complete Split Graphs1371509600610.22052/mir.2019.194302.1156ENPavel HicFaculty of Education, Trnava University, Trnava, SlovakiaMilan PokornyFaculty of Education, Trnava University, Trnava, SlovakiaDragan StevanovicMathematical Institute, Serbian Academy of Sciences and Arts, Kneza Mihaila 36, 11000 Belgrade, SerbiaJournal Article20190714In the paper we consider a generalized join operation, that is, the H-join on graphs where H is an arbitrary graph. In terms of Seidel matrix of graphs we determine the Seidel spectrum of the graphs obtained by this operation on regular graphs. Some additional consequences regarding S-integral complete split graphs are also obtained, which allows to exhibit many infinite families of Seidel integral complete split graphs.http://mir.kashanu.ac.ir/article_96006_008d42d57388103d76d5c846438d165c.pdfUniversity of KashanMathematics Interdisciplinary Research2538-36394220191201Oboudi-Type Bounds for Graph Energy1511559693810.22052/mir.2019.207442.1172ENIvan GutmanFaculty of Science, University of Kragujevac, P. O. Box 60, 34000 Kragujevac, SerbiaJournal Article20191103The graph energy is the sum of absolute values of the eigenvalues of the (0, 1)-adjacency matrix. Oboudi recently obtained lower bounds for graph energy, depending on the largest and smallest graph eigenvalue. In this paper, a few more Oboudi-type bounds are deduced.http://mir.kashanu.ac.ir/article_96938_35e2a0e7a15dcdd1e796325b33542469.pdf