Robert T. Tunis is a vice chairman at Colliers International, a commercial real estate services firm. He joined the firm in 1996, when it operated as GVA Williams. Tunis has advised clients on property transactions that add up to over $4.8 billion. His deals have included the leasing of 135,000 square feet for Donovan Data Systems, 151,000 square feet for PNC Bank, 522,000 square feet for Google, 35,000 square feet for National Bank of Canada, 88,000 square feet for Moses & Singer LLP, and 134,000 square feet for Legal Aid Societys NY Headquarters. CoStar Group, Inc., the commercial real estate information and marketing provider, named Tunis one of New York Citys top brokers. In 1990, Falcon Press published a book on commercial real estate written by Tunis, titled Plan of Attack. Tunis has a BA from Hunter College.  -MK