Unfortunately, I couldn't find a direct link to a PDF of the article. However, I can suggest some possible sources where you might be able to access the article:
: Changes occur at distinct points in time (events), such as a bank teller serving a customer or a part arriving on a factory floor. System Studies system simulation geoffrey gordon pdf
The text establishes a framework for modeling complex systems where events occur at distinct points in time. Unfortunately, I couldn't find a direct link to
Why should a modern engineer or data analyst spend time with a 50-year-old PDF? system simulation geoffrey gordon pdf
Modern Python (SimPy):