My undergraduate thesis (1974) advisor was Dr. Barbara Liskov who was designing CLU, which became a very influential research language. The first thing she told

My undergraduate thesis (1974) advisor was Dr. Barbara Liskov who was designing CLU, which became a very influential research language. The first thing she told me to do was to read a small book, Structured Programming by Dahl, Dijkstra, and Hoare. She particularly wanted me to read the chapter by Dahl on Sumula-67. Simula was an important contribution to the development of modern programming languages, by way of Sumula -> CLU -> Alphard -> Ada -> Modula -> C++ -> Java, and the many other connections back to Simula like Smalltalk.