“…For simplicity in (5.18) we may take U 1 = 1 and U 2 = c, some constant; then the necessary and sufficient condition for the reduction algebra to be isomorphic to the harmonic oscillator algebra becomes (5.19) |g 0 (x 0 , x 1 )| 2 = (α 0,0 x 0 + α 0,1 x 1 ) + c P k 0 (x 0 )P k 1 (x 1 ) , which implies that (5.20) g 0 (x, y) = exp(iθ) (α 0,0 x + α 0,1 y) + c P k 0 (x)P k 1 (y) 1 2 . Now let us look at a particular example given in [17], where H = h 0 (a * 0 a 0 , a * 1 a 1 ) + g 0 (a * 0 a 0 , a * 1 a 1 )a k 0 0 a * k 1 1 (5.21) +a * k 0 0 a k 1 1 g 0 (a * 0 a 0 , a * 1 a 1 ), with the matrix elements (5.22) α 0,0 = 1 k 0 , α 0,1 = 0, α 1,0 = k 1 , α 1,1 = k 0 .…”