Hyperquarks and generation number
Alfons J. Buchmann, Michael L. Schmid · Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D. Particles and fields · 2005
In a model in which quarks and leptons are built up from two spin-$\frac{1}{2}$ preons as fundamental entities, a new class of fermionic bound states (hyperquarks) arises. It turns out that these hyperquarks are necessary to fulfill the 't Hooft anomaly constraint, which then links the number of fermionic generations to the number of colors and hypercolors.