Hi Francesco11
I guess it depends on the purpose of the citation. Most people still cite the 2011 paper as it describes the iolite approach of using splines, selections etc. Although it does describe the software as freeware (which it was at the time) it's more about providing a reference to the data reduction approach of using time-series operations rather than reducing each sample to a single value (even if it doesn't explicitly say this).
Joe and I appreciate the citation, and if you mentioned that you received the student licence for free in the acknowledgements, that would extra appreciated. 😄
If you have used the 3D Trace Elements DRS, there is a new paper describing that. Similarly, if you used the CellSpace approach to mapping, there is a paper explaining that here. If you used the VizualAge plugin for U-Pb, you could cite Joe's paper describing that.
The second citation is probably because you used the "Image by Selections" approach to creating images. Not many people know this, but the first version of iolite was invented by John Hellstrom, a post-doc at UniMelb. That paper was the first regarding iolite and if you use some of the most fundamental parts of iolite, you may get a suggestion to cite that paper.
If guess whether you use a citation or an acknowledgement is up to whether you're describing how something was processed, or just providing information about where something was obtained. Most people cite the 2011 paper just like you would cite a lab procedure such as "samples were processed according to the protocols described by Smith et al."
Thanks for your question, we appreciate you asking.
Kind regards,
Bence