A tertiary audience member could be any number of unanticipated persons or a group of people (especially outsiders) who gain access to a document you have prepared for another person. 

Emojis and texting abbreviations are acceptable in workplace writing.

APA and MLA are the most widely used documentation methods for identifying outside sources or research used in a document, but there are many other styles or methods.

Plagiarism is acceptable in workforce culture. 

A cover letter is just a more specific form of the general business letter. The cover letter includes 

He robbed his apartment neighbours.

Professional resumes typically contain

У волшебника была волшебная палочка

All of these are standard forms of business communication:

Cover letters should be written with a future focus on the employer and position, not with your own interests at the forefront. What can you do for your future employer? How can your skills benefit a company or organization if you are hired?