“…al. [9], Chơn and Hà [11], Crossley [14], Hà [15], Hưng [19], Minami [26], Nam [31], the present author [41,42,43,44,46,47,48,49,50,51], Sum [61,62,63,65] and others). In [55], using the invariant theory, Singer claims that T r d is an isomorphism for d = 4 in a range of internal degrees, but T r 5 is not an epimorphism.…”