If you read the official Elsevier copyright and trademarks statement on the company webpage, the language seems to indicate that you need to to keep the ClinicalKey logos intact if you use the presentation maker features. However, the library has confirmed with the publisher that while you need to cite the source of your content, you do not need to preserve the trademarked logos indicating which publishing platform for the journal article, image, or ebook. Copyright protections and citation conventions dictate that you cite the source - not the platform for the source.