... Inofficial Mathematical Chemistry page by Eugene V. Babaev Moscow State University, Russia . ... Section 2 recalls several concepts of the graph theory and topology of surfaces, necessary for further discussion, and Section 3 is the overview of the common types of molecular graphs and molecular surfaces used in chemistry. ... The objects are some specific molecules with bipartite graphs (which follow so-called "alternation rule", and the operation is a polar chemical reaction. ... Chemistry . ...