Verizon ( VZ) took another step toward the divestiture of its telephone directories business Friday, filing a form 10 with the Securities and Exchange Commission that clears the way for a potential spinoff. Verizon, which said it was exploring alternatives for the directories unit in December, said it has yet to decide on exactly what form the separation will take. The New York phone company did say, however, that it expects some type of transaction -- a spinoff, sale, or combination -- will close by the end of 2006. The Dallas-based unit houses Verizon's domestic print and Internet yellow pages and employs 7,100 people. For 2005, it earned $1.75 billion before interest, taxes, depreciation and amortization, on sales of $3.45 billion. All told, the unit is believed to be worth about $13 billion. Verizon closed at $33.02 Thursday.