Paperbacks and hardbacks may be attached to the same bibliographic record only if they meet the OCLC Bibliographic Formats and Standards match criteria.
An ISBN on a matching item should be added to the bibliographic record if not already present. See also the SHARE cataloging standard: Guidelines for retaining ISBNs in a record.
In cases where the presence of a hardback or paperback edition statement is the only difference, and the books otherwise meet the criteria for being attached to the same record, both edition statements may be included in the Polaris record.
Transcribe both edition statements in one MARC tag 250, separated by a comma.
250 _ _ $aFirst hardback edition, 1st paperback edition.