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A cover letter is a one-page persuasive document you may submit along with a résumé or curriculum vitae (CV) as part of a job application. It's typically your first chance to introduce yourself to and establish a connection with a prospective hiring manager.
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A strong résumé contains information about your suitability for a specific position through strategic organization and descriptions of your experiences.
A strong cover letter provides more detail on details specific experiences, knowledge, skills and values included in your résumé that you want the employer to know more about.
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