Hi Jeevan,
Apologies for the very late reply. If you’re looking for a Black Belt guide, the place to start is the exam you’re planning to take, because each certifying body publishes its own Body of Knowledge:
Each page walks through the topics on that exam, with links to free articles on each one. If you haven’t picked a certification yet, my article on the most recognized Six Sigma certifications will help you choose.
To see where you stand, the free Black Belt study guide includes a 75-question practice exam with explanations. There’s also a full Black Belt study guide if you want everything in one place.
Tell me which exam you’re aiming for and when, and I’m happy to point you further.
Ted