Seeking info on Nannies

My husbands sister passed away a couple of months ago leaving three small kids with out a mom, well as a family we have been helping watch the kids and my brother-in-law has decided to look into getting a Nanny to help things be more consistant. Great idea I think.

Does anyone know of where we could look into getting a good Nanny and where should we look into finding one? Or any other information that might be helpful in this area would be grateful. Thanks