Calcium, Mg and dKH Explained
 

http://www.advancedaquarist.com/2002/11/chemistry

This link is perhaps the best article I found explaining in clear English how to balance calcium, hardness(dKH), magnesium and pH.

The four part graph is very useful.

Thank you for the link. You were right, it's one of the easiest to comprehend articles I've read regarding the subject.