On the non-polar variation in the mean latitude

It is pointed out that (1) the equations used by Yumi and Wako [1] and by Okuda [2,3] to calculate the non-polar variations in the latitude of stations, are equivalent, and either set by itself gives only indeterminate solutions. (2) The solutions given by these authors depend on the assumptions made and the assumptions lack sufficient bases. Their results are therefore unreliable. (3) Although the authors managed to make (o-c) and $\text{Δ}\text{z}$ to approach zero their calculations, this does not prove that their results are correct.