Kenneth G. Wilson (1923–). The Columbia Guide to Standard American English. 1993.
think (n., v.)
The verb think combines with to plus an infinitive, particularly but not only in the negative, as in I didn’t think to ask and I thought to speak to her about it, but I forgot. In such uses the meaning is “remember, expect, or intend to” and is Standard. Also Standard is He didn’t think she’d mind, just as is He thought she wouldn’t mind. The noun think is a result of functional shift and is Conversational and Informal: I’ll give it a good think tonight. See BELIEVE; RAISING.
