Hi Reza apologies for the delayed response here! I hope this answer can still be helpful to you and others with similar questions.

Lucid is supportive of the use of our software in your materials. If you created the document you would like to use yourself then you are the owner of the diagram and can use it however you would like. Others who have used diagrams in books or publications have cited the diagram image with "Created in Lucid (lucid.co)". We encourage you to do this as well but it is not required as you own the work you created in Lucidchart.

If you would like to use a template we created you may reference us with the following citation: Created in Lucid (lucid.co)

If you would like to reference an article or webpage we wrote you may reference us like this:
“Article name.” Link to asset
For example: “How to Use Value Stream Mapping in DevOps.” www.lucidchart.com/blog/value-stream-mapping-for-devops

We also ask that you reference/cite any product screenshots as “Lucid lucid.co” or other wording that references both our full brand name and our website.

Please let me know if you have any further questions.