pop culture references are common , as are mentions Statement of memes , classic science fiction movies , and other geek/nerd mainstays .

The poster and logo for the tour included Cause_to_be_included references to Kabbalah , which Madonna studied Education_teaching .

Obama and others paid Commerce_pay homage to Lincoln in the form of tributes and references during several of the events , starting Process_start with a commemorative train tour from Philadelphia , Pennsylvania , to Washington , D.C. on January 17 , 2009 .

Figures in the table derive Creating from the latest references below , as casualty numbers are the subject of dispute Quarreling .