Prof. Dr. Matthias F. M. LutzTU DarmstadtInstitut für KernphysikSchlossgartenstr. 964289 Darmstadt
Partly it is not possible to calculate the full theory. This is where the lattice gauge theory comes into play.
Usually hadrons consist of 3 quarks or a quark-antiquark pair. But theoretically also states with four quarks are conceivable.