Journals of the House of Burgesses of Virginia By Virginia. General Assembly. House of Burgesses, Virginia State Library
Can't link Pettiplace to the tree, but when someone does, this source shows that he was a Burgess of the Assembly in 1632, for Denbigh and Waters Creek.
The book is downloadable as a pdf from Google books or can be purchased as an e-Book for most reading devices. Got my fingers crossed that Santa is bringing me a Kindle this year.