gistfile1.txt

    ## Specify the journal's ISSN(s) for journal-specific styles. An ISSN
    ## must consist of four digits, a hyphen, three digits, and a check
    ## digit (a numeral digit or roman X), e.g. "1234-1231".
    element cs:issn { issn }
  info.eissn =
    
    ## Specify the journal's eISSN for journal-specific styles.
    element cs:eissn { issn }
  info.issnl =
    
    ## Specify the journal's ISSN-L for journal-specific styles.
    element cs:issnl { issn }