Write a question about the following article: While working for his PhD, he collaborated concurrently with the Swiss urban planner Professor Arnold Hoechel and the architects Frei and Hunziker on several projects, including the first automatic bowling alleys in Meyrin Commune, Geneva, and Beirut, Lebanon. In 1961, he returned to Tehran as Deputy Technical Director of Iran-Rah, the largest Construction Co. of its time in Iran. In 1963, he created his own firm under the name of Borbor Consulting Architects, Engineers, City Planners. As President and managing director, he developed and expanded the business to a large multidisciplinary organization with several in-house departments which included: architecture, urban planning, environment, structure, mechanics, electricity and interior design. The firm employed a large number of highly qualified multi-national staff and included branch offices in several major cities in Iran. A few months prior to the 1978 Iranian Islamic Revolution, Borbor moved to Paris, France where he founded the Borbor International Management Consultants  to Architects, Engineers, Planners. BIMC offered consultancy services in design, management and documentation to architectural and planning firms. In 1984, he moved to Los Angeles where he was involved in some architectural consultancy and research on Iranian and Persianate subjects. Borbor returned to Iran in 1991 and established the Research Institute and Library of Iranian Studies , a non-profit, non-political, private and independent institution dedicated to the promotion of research in the field of Iranian and Persianate studies with special emphasis on novel and creative research

Question about the article:
How many years after the Iranian Islamic Revolution did Borbor go back to Iran?