You are invited to a free one-hour informational seminar about protecting historic buildings. Preserving an historic structure could benefit the Back Bay and may result in a tax deduction. Boston Public Library, 700 Boylston Street, Boston.  Register today by calling Mory Bahar, a representative of the Trust for Architectural Easements, at 978-352-5615, or by sending an email to mbahar@architecturaltrust.org.  For more information, log on to www.architecturaltrust.org.