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This is a re-creation, with minor corrections of Ramos, et. al.'s harmonic simulation published in their 1993 paper, "A Simplified Harmonic Simulation Procedure", availble through the IEEE.
The use of harmonic current distribution factors at each bus is unique to the method presented by Ramos, et. al., it seems to be in concert with the intent of IEEE 519 but is not explicitly discussed in the standard.
The paper does provide a solid review of developing the admittance matrix for a small radial distribution system and solving for the bus currents and voltages by matrix methods.