The Mayor of Trenton is restoring some services at four library branches that were closed 20 months ago because of budget cuts. The first of the so called learning centers has opened in Trenton’s South Ward, allowing residents to read books and use computers to get information on the Internet.Mayor Tony Mack says each center will have two part-time employees and a security guard, but most of the staff will be volunteers.”It’s what we have to do under the circumstances. Our aid from the state was cut by some $27 to $30 million over the last two years. So we’re making due with what we have.”Mack says local grants will help pay the $240,000 cost to operate the learning centers. He says it’s a model other cities might follow. The New Jersey Library Association says the funds should be used to restore hours to the existing public library system.