For e-mail, get the writer's permission to use his/her words. Remember to print off a copy of the e-mail for verification of the information as e-mail messages are not available to others. Style manuals give a sample of citing e-mail in reference lists.
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Yes. Ask the person you are interviewing for permission to use their conversation before you start the interview. Their discussion with you should be credited to them since you are using their ideas. Make sure you include the appropriate citation for interviews.
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