12.21Secondary dominant notation looks intimidating but is simple

Suppose:

V7/ii

Read from right to left.

ii = the target.

In C, ii = Dm.

What is V7 of D?

A7.

So:

V7/ii = A7

Another:

V7/V

Target = V.

In C, V = G.

Dominant of G = D7.

So:

V7/V = D7