Citation is a complex hybrid of various stone fruit bred by Zaiger.

Lovell is a seedling peach, ie grown from seeds of Lovell peach.

Krymsk is probably a hybrid of various stone fruit that was bred in Russia.

Fruitnut! Finally. I've searched the web and this really helps. Thank you so much. My apricot tree that snapped in the hurricane was 'Harglow' on Lovell. Lovell through out many suckers. If I let the rootstock grow, it would become a peach tree? Mrs. G

I've always wanted to know what Citation was so I did some looking...it looks like a plum/peach hybrid:

link

University of California has a lot of rootstock trials that you can look through...

link