Eugene L. Mittelgluck, 90, who had served as director of Mount Vernon (N.Y.) Public Library and New Rochelle (N.Y.) Public Library, died April 21. As director of New Rochelle Public Library, he oversaw construction of a new main library that won an American Institute of Architects and ALA Award of Excellence for Library Architecture in 1980. After retirement, he served as interim manager at Bronxville (N.Y.) Public Library and as a librarian at Yonkers (N.Y.) Public Library.