In an expansion of the bookstore battle over vertical integration that has spread to the comic business, PW Daily is reporting that two chain book outlets have dropped titles published by Sterling, the trade publisher recently acquired by Barnes and Noble.  While both Borders (see 'Viz Gives Borders-Waldens Di Gi Charat Exclusive') and Barnes and Noble ('Barnes and Noble To Publish Masterworks TPBs') have been doing exclusive deals to be able to offer titles that the other does not, Barnes and Noble had hoped that rival chains would continue to carry its Sterling titles.  But Borders and Costco both told PW Daily that they would no longer carry books from the Barnes and Noble-owned publisher.