Firstly, subject selection is always tricky. When you are chosing subject i suggest you to chose in such a way that you get maximum commonality between your Css subjects and PMS. This will synergises your effort competitive exam.

Secondly, read course outline painstakingly and try to consult relavent subject expert about minimum books that can cover whole syllabus of the aformention subject. If that subject takes only one book to cover whole syllabus then i suggest you to chose him but before taking final decision also consider length of the course. Both things will help you to keep your relevency intact and also saves your most of the time.

Thirdly, chose subjects which are according to your education. It will help you alot in many ways.

Lastly, there is no shortcut in css/pms. You have to put all your efforts sincerely and efficiently.

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