[en] A theory of several fermion fields interacting with several scalar fields is suggested. The model is nonlocal and is partially solvable under arbitrary choice of its form factors. The latter are shown to determine the resulting fermion-fermion interaction. The observable ('clothed') bosons of the model have the properties of the cosmological 'dark matter' and cannot be detected in earth laboratories. This is the exact result of the model. Meanwhile in QCD the invisibility of isolated gluons is explained by using additional hypothesis of colour confinement