Professor Cornelis J. Elsevier works at the "Universiteit of Amsterdam". He did not exist at Wikidata and there was only one paper to be found for him.
Adding this one paper was done with the "Resolve Authors" tool. The Scholia tool for Mr Elsevier showed a few co-authors and in addition to this several "missing co-authors" could be found.
In order to show more papers for Mr Elsevier, more papers needed to be imported into Wikidata. This can be done for authors with an ORCiD identifier, particularly the ones with no known gender. So far they did not get much TLC. Just running the "SourceMD tool" for them will add additional papers and associate other authors to these papers as well.
This is an iterative process and I focused for no particular reason on Mrs Barbara Milani. Processing her co-authors meant that more co-authors came out of the woodwork. At this time, 13 new authors with an ORCiD identifier popped up. Once they are processed more papers will be known to Wikidata and given their relation to Mrs Milani a reasonable chance that these papers link to Mr Elsevier as well.
At this time Mr Elsevier is known to have 7 publications.