Beck, Robert Mark (1960년 12월 30일). 《PB-250 - A High Speed Serial General Purpose Computer Using Magnetostrictive Delay Line Storage》. 《Managing Requirements Knowledge, International Workshop on (AFIPS)》 (영어). 284–285, 287쪽. doi:10.1109/afips.1960.58. The first production computer was delivered in October 1960.
ed-thelen.org
Weik, Martin H. (Mar 1961). “PACKARD BELL 250”. 《ed-thelen.org》. A Third Survey of Domestic Electronic Digital Computing Systems.