his sons' architecture firm
... that I. M. Pei said that his sons' architecture firm "came of age" while designing the Bank of China head office in Beijing?
... that <a href="./I._M._Pei" id="mwAUc" rel="mw:WikiLink" title="I. M. Pei">I. M. Pei</a> said that <b id="mwAUg"><a href="./PEI_Architects" id="mwAUk" rel="mw:WikiLink" title="PEI Architects">his sons' architecture firm</a></b> "came of age" while designing the <a href="./Bank_of_China" id="mwAUo" rel="mw:WikiLink" title="Bank of China">Bank of China</a> head office <i id="mwAUs">(pictured)</i> in Beijing?