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The diagrams are free for you to use for any purpose.
Please contact me with any questions, comments, suggestions, ideas for new diagrams, etc.
Customization - adding titles, text, etc.
You can use the PNG version as a background image in your word processing program. The specific instructions for this will vary depending on the proram you use. Look for instructions on adding a background image or watermark. Then you can write anything you want right on top of the image.
Also, you could use the PNG image as a background in a drawing program - then you could add lines, etc.