Color confinement is a foundational principle of quantum chromodynamics stating that color-charged particles like quarks cannot exist in isolation, making this a matter of definition and standard scientific observation requiring no specific citation.
The claim that quarks cannot be separated indefinitely due to color confinement is a core, universally accepted definition within quantum chromodynamics (QCD) and everyday physics instruction. While the retrieved papers discuss broader aspects of QCD, lattice calculations, and hadron physics, the principle itself is foundational knowledge that does not depend on a single contested study. Therefore, it is classified as common knowledge.