Law doubt

Dear friends, I am studying CPT law. In the book, for suppose, it has been mentioned that the term "Express contract" is defined in section 9 of the Indian contracts act 1872. But in the case of "Implied contracts" and "Quasi Contracts" there is no mention about the sections where these terms have been given in the original act. Not only in the context of these defintions, but repeatedly it is happening in other defintions too. For some defintions they are mentioning the acts and for some other they are not. Even i have searched for them in the original act too. But i was unable to trace them. so please clarify about from where these unmentioned defintions are taken.