How to reference original paper in expanded journal version Many journals allow to submit an extended version of a conference paper as, for example, Springer:


  Expanded versions of papers which have previously appeared in
  conference proceedings will be considered and this request must be
  made at the time of submission; the authors must clearly state the
  conference publication and provide a statement of revisions/updates
  that have been made to the journal paper.


When writing such an extended version how do you reference the conference paper? I can imaging several possibilities:


Treat it like every other paper in related work
Ignore the conference paper completely and present all results as if for the first time.
Clearly indicate that you wrote the conference paper as "... in [1] we showed that and shortly review the approach ..."


What is correct way to write an extended journal (in CS)?
You write the journal version so that it is entirely self-contained, as if all results were new (regardless of whether they were already present in the conference version).

Then, in appropriate places, you refer to the conference version and explain how the current version is different. For example, you could have a footnote on the first page or an acknowledgement in the end of the paper, along these lines:


  This is an extended and revised version of a preliminary conference report that was presented in FOO 2015 [1].


Here [1] is a reference to the conference version, and you include it in the list of references as usual. There is no need to cite it elsewhere.

If it makes sense, you can also discuss the difference between this version and the conference version in more detail e.g. in the "Related work" section. This might be a good idea especially if the journal version is not just an extension but some results are fundamentally different. However, in straightforward cases this is not usually necessary.



(Please note that this answer is specific to computer science, which has its own peculiar approach to conference publishing. All other fields are different.)