“…Closest to the present approach are those papers that use only quantum mechanics, relativistic or nonrelativistic, and are written in the spirit of Feynman's demand for simplicity. These papers nevertheless contain one or several of the following restrictions: the wave functions must have special invariance [11,12], continuity [13][14][15][16][17] or symmetry [18] properties, or must lie in special spin-component subspaces [19]. The systems considered must be nonrelativistic [13][14][15][16][17][18][19][20][21][22], have only two spatial dimensions [22], contain only two particles [18,19], only particles with zero spin [13][14][15][16][17] or spin ≤ 1/2 [20,21], only point particles [23][24][25], must admit antiparticles [26], or the exchange must be considered as physical transportation of real objects [11,12,[23][24][25]27].…”