I recently presented a paper at a conference which was published in its proceedings. Now it is time to submit an "extended" version with "30% new content". The new content isn't a problem, I've added several figures, a couple of genuinely new findings and some helpful illustrations that I developed while preparing my talk. However, the instructions from the publisher state:
In the extended paper clearly cite the conference paper and list it as one of the references.
In my opinion, this can be interpreted in one of two ways:
- Write a new article that assumes knowledge of the proceedings. This is kind of a scary option because it implies that it really has to be a new work.
- Explain that an earlier version exists and what's new here. This is a comforting interpretation but seems kind of uncharacteristic for the style in most journal articles.
What's the best path to follow here?