Houghton Mifflin Harcourt 

month
2012 2013
  • January 44
  • February 20
  • March 36
  • April 69
  • May 36
  • June
  • July
  • August
  • September
  • October
  • November
  • December
2011 2012 2013
  • January 67
  • February 71
  • March 66
  • April 99
  • May 78
  • June 62
  • July 72
  • August 77
  • September 54
  • October 51
  • November 50
  • December 27
2010 2011 2012
  • January 26
  • February 44
  • March 68
  • April 77
  • May 67
  • June 49
  • July 56
  • August 46
  • September 37
  • October 38
  • November 32
  • December 67
2010 2011
  • January
  • February
  • March
  • April
  • May
  • June 21
  • July 27
  • August 23
  • September 40
  • October 74
  • November 35
  • December 35