Help with odd number dividers

[ekdin]

I am reading this:
https://www.onsemi.com/pub_link/Collateral/AND8001-D.PDF

On page three, the logic equations is given for the divide-by 9 DFF circuit. How do I obtain the equations through k-maps? I know to use k-maps, but I dont know what and how they filling the k-maps with to obtain:

Ad = A*B* Bd = A*B + AB*
Cd = ABC* + CB* + A*C Dd = ABC

Any illustrations appreciated.

 

[DigitalLogician]

You should first turn each Boolean equation into a truth table, then if you need help turning a truth table into a K-map and beyond, go to **broken link removed**. The particular page is about BCD to Excess-3, but it has an article that converts a truth table into k-maps. The circuits there are all interactive.