Why are some of my article referenced on Scholar google, and some other ain't?

Software Support
2

I tried the sitemap trick mentioned here: [OJS 2.3.1.2] Indexing journal system to Google Scholar

But our installation has so many articles that I have no way of tracking how it worked.

Make sure that you have google scholar plugin and duplin core plugin enabled.

In the end I think that the same thing applies to Google Scholar as the rest of Google: you basically never know how exactly google is indexing.