Examples of fields and data used for electronic version of a book that was issued in paper also:
300 bb 1 online resource (1 v.) ---OCLC 663096952
300 bb 1 online resource (x,324 p.) : $b ill. ---OCLC 780425969
655 b4 Electronic books [genre heading]
Field 260 with 2 publishers over different time periods (OCLC no. 32886840)
$3 <'93-'95>: $a Dordrecht ; $a Boston : $b Kluwer Academic Publishers
$3 <2009->: $a Dordrecht : $b Springer
Field 362 for serial holdings (OCLC no. 713316046)
362 1b Began with v. 1, no. 1 (Mar. 2011).
Field 300 for description of CD-rom
xvi, 640 p. ; $c 26 cm. + $e 1 CD-ROM (4 3/4 in.)