Abstract
Study material contains the outline of main information entities persistent identifiers, which are used globally in information systems. In two chapters both persistent international standard identifiers and other persistent identifiers for online digital resources are presented.
The international standard identifiers are arranged into groups accordings to FRBR/IFLA model (information follows up and completes published FRBR/IFLA model). The text and figures present the continuing of development of complex world network of persistent identifiers.
Information comprised in brief characteristics of each identifier originates from both international standards or internet RFC standards, and from other public available resources.