Does "between each other" the correct term in this sentence?

Hi,

Does "between each other" the correct term in this sentence?

"Extra analysis was accomplished to examine any significant relationships between attitude(1), willingness to purchase (2), the necessity of labeling GMFs (3), and demographic variables, and between each other."

To explain a bit more:

We have examined if there is any relationship between (1), (2), and (3) from one side, and "demographic variables" from another.

Also, we have examined if there is any relationship between (1), (2), and (3)"

Thanks!