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Behavior Over Time
Explanation of Behavior Over Time diagrams is in the book Connection (chapter 7)
It states what Behaviour Over Time diagrams are and what the intention and methods are. There are also many examples.
It is often wise not to make Behaviour Over Time diagrams digitally. Drawn by hand and provided with your own symbols/drawings is often the best. However, for presentations and/or inclusion in books or articles, a digital version is sometimes preferred.
In that case you can use THIS model. (Office, Ecxel)