The advances in technology and development of internet have fundamentally changed both publishing process and methodology of scientific information search. Often it is difficult to find a certain publication despite existence of scientific journals own websites. To solve this, in the late 90's the use of digital object identifier (doi) was proposed by CrossRef. Doi is working as permanent hyperlink that would link to required web pages even after change in the web site structure. Since then, the index has been widely used by scientific publishers, as well as scientists. Additional services that are offered by CrossRef, now became mandatory for the high sited journals. Unfortunately, to date, only two Ukrainian journals are fully using doi, also several is using it only for English versions republished abroad. The aim of this article is to introduce doi, describe other services proposed by CrossRef and give practical advice for the journals. (Article in Russian)