D. Bonatsos, C. Daskaloyannis, P. Kolokotronis, και D. Lenis, ‘Nonlinear extension of the u(3) algebra as the symmetry algebra of the three-dimensional anisotropic quantum harmonic oscillator with rational ratios of frequencies and the Nilsson model’, HNPS Adv Nucl Phys, τ. 5, σελ. 14–28, Φεβρουαρίου 2020.