Plagiarism - posting the work of others with no indication that it is not your own - is frowned on by our community, and may result in your content being downvoted or deleted.
If you copy (or closely rephrase/reword) content that you did not create into something you post on MathOverflow (e.g., from another site or elsewhere on MathOverflow), make sure you do all of the following:
- Provide a link to the original page or answer
- Quote only the relevant portion
- Provide the name of the original author
This ensures that the original creator gets credit for their work.
According to Ernest Hemingway - Biographical on Nobelprize.org, Hemingway saw combat when he was a teenager. It says:
After the United States entered the First World War, he joined a volunteer ambulance unit in the Italian army. Serving at the front, he was wounded, was decorated by the Italian Government, and spent considerable time in hospitals ....
[other sources, quotes, explanations, etc. necessary to complete the answer]
Do not copy the complete text of sources; instead, use their words and ideas to support your own. In particular, answers comprised entirely of a quote (sourced or not) will often be deleted since they do not contain any original content.
Always give proper credit to the author and site where you found the text, including a direct link to it. For non-web-based citations, include the source to the best of your ability (title, author, page number, etc).