found: LC manual cat., 3/18/99: hdg (Houghton Mifflin Company; in use after 1908?)
found: The American Heritage essential student thesaurus, 2010: ECIP application (company name is no longer Houghton Mifflin Company, but Houghton Mifflin Harcourt Publishing Company)
found: Email from pub., May 5, 2010 (masthead of our website abbreviates our company name to just Houghton Mifflin Harcourt ... bottom of our website ... copyright line, as well as in the ownership line (relating to EMPG), the company's name is spelled out as Houghton Mifflin Harcourt Publishing Company)
notfound: Wheeler, H.N. Argument against the passage of the Loud Bill, 1897: t.p. (Houghton, Mifflin and Company)