the design and execution of that historic facade took place remains uncertain. Paolo Sanpaolesi (1963), seconded by Brenda Preyer (1981), proposed a two-phase facade construction, with the first (c. 1450), equal to five bays, covering the exteriors of the old dwellings of Giovanni and his mother and then a later two bay expansion to cover the house added in 1460. That Rucellai never managed to add the next house in the row to his holdings would account for the facade remaining unfinished and one bay short of the eight intended. Mack (1974), together with by Kurt Forster (1976) and Howard Saalman (1966) have interpreted the evidence differently, arguing that that work on the facade would have awaited the acquisition of the third property along the Via della Vigna Nuova and was stimulated by the engagement of Rucellai's son Bernardo to Piero di Cosimo de' Medici's daughter Nannina in 1461. According to this theory it could only have been after the betrothal, that the pairing of clearly identifiable Medici devices with those of the Rucellai in the friezes could have been permissible. The same is case for the Medici interlocking rings insignia that occupy the spandrels of the windows. That would postpone construction of the Rucellai facade to a date after 1461 and calls into question its primacy over the almost identical design used for the Palazzo Piccolomini (designed by Bernardo Rossellino 1459-62) in the papal city of Pienza. Authorship That post-1461 dating raises once more the question of authorship. Based upon the word of Giorgio Vasari and some other mid-to-late-16th century comments as well as upon Giovanni Rucellai's known use of Leon Battista Alberti as the architect of his chapel in the neighboring church of San Pancrazio and for the completion of the facade of Santa Maria Novella, the great humanist scholar and artistic theoretician commonly has been accepted as having been responsible for the design of the Rucellai Palace's facade. However, the first comments on the facade, made in the early 16th century do not mention Alberti but rather link it to Bernardo Rossellino by saying that he had made the model for the palace. That might mean that he was responsible for the facade or simply that he had furnished a model following someone's directions (i.e., Alberti). The first to doubt Alberti's role as the architect was Julius Schlosser who wrote (1929) that "It is Bernardo Rossellino's spirit