Max E. Sime Thomas R. G. Green D. J. Guest Psychological Evaluation of Two Conditional Constructions Used in Computer Languages. 125-133 1999 51 Int. J. Hum.-Comput. Stud. 2 http://dx.doi.org/10.1006/ijhc.1972.0302 db/journals/ijmms/ijmms51.html#SimeGG99