I'm not sure what you mean about "the archives of this subject". If you mean the archives of this Ancestry.com Yocum discussion list, simply go to the searchable archives at:http://boards.ancestry.com/surnames.yocum/mb.ashx
If you mean the specific archives that contain the info on Mattheus Jochem and his sons in Edigheim, Pfalz, Germany prior to their emigration to the US, that can be found at the Family History Library in Salt Lake City, and abstracted in part on their website, FamilySearch.com. Oskar Poller published a book on the families of Edigheim which was compiled from the original church and civil records from the 1400s - 1800s. The Family History Library has copies of the original records as well as transcriptions (which are much easier to read!)
If you are a descendant of Matthias Yoakum/Mattheus Jochem, what is your line? Perhaps I can help point you in some helpful directions.