Кандидат на престол : из истории политических и культурных связей России и Швеции ХI-ХХ веков / Г.М. Коваленко. (OCLC #43227577)

MARC field 530 is a general note about the availability of additional physical or digital forms:

530 __ ǂa Also issued online.

More specific information goes into 776:

776 08 ǂi Online version: ǂa Kovalenko, G.M. (Gennadii
    ̆ Mikhaĭlovich). ǂt Kandidat na prestol. ǂd Sankt-Peterburg
    : Russko-baltiĭskiĭ informat︠s︡ionnyĭ t︠s︡entr BLIT︠S︡, 1999 ǂw 
    (OCoLC)60730009

Currently, MARC records in OCLC are created at the manifestation level, and this method can be used to link together different manifestations of the same expression.