@techreport{plt-tr2009-algol60-v4.2.3, author = {PLT}, title = {Algol 60}, number = {PLT-TR2009-algol60-v4.2.3}, type = {Reference Manual}, institution = {PLT Scheme Inc.}, month = {December}, year = {2009}, url = {http://download.plt-scheme.org/doc/4.2.3/pdf/algol60.pdf}, note = {\url{http://plt-scheme.org/techreports/}} }