I don't know where the proof is for something that I learned in kindergarten. This is such an elementary (and obvious) matter, though I appreciate that there may be some real bores out there who need proof for everything.
You could look in Swan. I don't have my copy to hand.
teachingCn wrote:now I need to find this situation quoted according to some kind of rule or quoted in some kind of "grammar dictionary" (i.e., Webster's Grammatical Dictionary or something of the sort).
But I can tell you for sure that you meant e.g. and not i.e., and the "proof" is here: http://eslblogs.englishclub.com/english ... /eg-or-ie/