I was looking through my grammars book by Daniel I.A.Cohem "Introduction to Computer Theory". Chapter 16 goes into depth on Pushdown Automata Theory with Chomsky Normal Form.
If L is a context-free language generated by a Context -free Grammar that includes A-productions, then there is a different context=free grammar that has no A-productions that generates either the whole language L or else generates the language of all the words in L that are not A.
If you never took grammars and after reading this were like what the..? A few pages later in the end of the proof, the author throws this great metaphor to help you understand the rules. I read it again and couldn't help laughing ...and enjoying:
Those never born need never die.
" With all the trouble in this world, it would be better if we were never born in the first place."
"Yes, but how many are so lucky? Maybe one in ten thousand."