Improved publications page.

publications.html

@@ -150,6 +150,7 @@ Hipparchus can also be cited with its own <a href="https://zenodo.org/records/84
 These publications are not directly related to Orekit. The purpose here is to share scientific works that makes use of Orekit and highlight the diversity of Orekit usages.<br/>
 So if you have used Orekit in your work and have published a paper on it, please consider sharing it here!<br/>
 There is a <a href="https://forum.orekit.org/t/scientific-documents-using-orekit/2780">dedicated thread on the forum</a> where you can contact us and share your references.
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