Sources for Biography

http://books.google.com/books?id=JyoEAAAAYAAJ&pg=RA1-PA129&lpg=RA1-PA129&dq=alvan+g+clark+astronomer+biography&source=web&ots=cCsbvcICgo&sig=9cWddvFZl8h-1lQOZxHugOAmErc&hl=en

http://books.google.com/books?id=JyoEAAAAYAAJ&pg=RA1-PA129&lpg=RA1-PA129&dq=%22alvan+g+clark%22+astronomer+biography&source=web&ots=cCsbvcIDhh&sig=HimqGhqFjTulemprQnCuaBYzqTM&hl=en

http://books.google.com/books?id=uCszAAAAMAAJ&pg=PA433&lpg=PA433&dq=%22alvan+g+clark%22+astronomer+biography&source=web&ots=ZPDGuP_Fp8&sig=71X7yQjMHIs7li3tOuSl43tGt8w&hl=en

http://infomotions.com/etexts/gutenberg/dirs/1/5/8/2/15824/15824.htm