isbn 0816511489 also sky publishing corporation march 2006==liên kết ngoài==*many biographical articles on clyde tombaugh*quote from tombaugh on ufos*ufo activities of tombaugh*academic paper on tombaugh's ufo activities and nearearth satellite search* illinois proposes a pluto day and reinstate pluto as a planet in honor of c tombaugh illinois general assembly senate resolution sr0046 2/26/2009