I am currently in charge of marketing/advertising for our upcoming production of "I Love You, You're Perfect, Now Change."  For the radio ads, I would like to use a teaser comprised of some lines from the opening of the musical.  My question is:  Is there a limit on the number of lines that can be used?  And, if there is, how do I go about getting permission to use the lines?  Thanks in advance for any help any one can offer.