When a verb follows another verb, it takes the form of either gerund or an infinitive. But we sometimes see sentences as below:<br/><br/>Come see me when you can.<br/>I go study in the library every afternoon.<br/><br/>I also read somewhere that sentences as below are grammatically incorrect:<br/><br/>John goes study in the library every.<br/><br/>Please clarify. And how about the sentence below, is it correct to say:<br/><br/>The promotion campaign helps double the sales.