Instructions: In this task, you're expected to write answers to questions involving multiple references to the same entity. The answer to the question should be unambiguous and a phrase in the paragraph. Most questions can have only one correct answer.
Input: Passage: Ieoh Ming Pei, FAIA, RIBA (born 26 April 1917), commonly known as I. M. Pei, is a Chinese American architect. Born in Guangzhou and raised in Hong Kong and Shanghai, Pei drew inspiration at an early age from the gardens at Soochow. In 1935, he moved to the United States and enrolled in the University of Pennsylvania's architecture school, but quickly transferred to the Massachusetts Institute of Technology. He was unhappy with the focus at both schools on Beaux-Arts architecture, and spent his free time researching emerging architects, especially Le Corbusier. After graduating, he joined the Harvard Graduate School of Design (GSD) and became a friend of the Bauhaus architects Walter Gropius and Marcel Breuer. In 1948, Pei was recruited by New York City real estate magnate William Zeckendorf, for whom he worked for seven years before establishing his own independent design firm I. M. Pei & Associates in 1955, which became I. M. Pei & Partners in 1966 and later in 1989 became Pei Cobb Freed & Partners. Pei retired from full-time practice in 1990. Since then, he has taken on work as an architectural consultant primarily from his sons' architectural firm Pei Partnership Architects.
Pei's first major recognition came with the National Center for Atmospheric Research in Colorado (designed in 1961, and completed in 1967). His new stature led to his selection as chief architect for the John F. Kennedy Library in Massachusetts. He went on to design Dallas City Hall and the East Building of the National Gallery of Art. He returned to China for the first time in 1975 to design a hotel at Fragrant Hills, and designed Bank of China Tower, Hong Kong, a skyscraper in Hong Kong for the Bank of China fifteen years later. In the early 1980s, Pei was the focus of controversy when he designed a glass-and-steel pyramid for the Musee du Louvre in Paris. He later returned to the world of the arts by designing the Morton H. Meyerson Symphony Center in Dallas, the Miho Museum in Japan, the Suzhou Museum in Suzhou, Museum of Islamic Art in Qatar, and the Grand Duke Jean Museum of Modern Art, abbreviated to Mudam, in Luxembourg.
Pei has won a wide variety of prizes and awards in the field of architecture, including the AIA Gold Medal in 1979, the first Praemium Imperiale for Architecture in 1989, and the Lifetime Achievement Award from the Cooper-Hewitt, National Design Museum in 2003. In 1983, he won the Pritzker Prize, sometimes called the Nobel Prize of architecture.
Question: What is the last name of the person who established their own independent design firm?
Output:
Pei.