HMHC: That will be the stock symbol for iconic textbook publisher Houghton Mifflin Harcourt, which has filed for a $100 million initial public offering that analysts say can raise up to $250 million. The company, which dates to 1832, had seen its ups and downs, having most recently bounced back from bankruptcy last year. Boston Business Journal reports that HMH CEO Linda Zecher is aiming for digital sales to make up 50 percent of the company's revenue. (They currently constitute around 30 percent.) This year, the Boston-based company announced partnerships with the likes of Knewton and Samsung to expand its digital offerings and distribution opportunities.