Just because many people here ask what the reference letter needs to have and what not:
Proof must include a reference letter from former employer and pay stubs. The reference letter must:
be an official document printed on company letterhead
include your name, the company’s contact information (address, telephone number and e-mail address), the signature of your immediate
show all positions held while employed at the company
include these details: job title, duties/responsibilities, job status, the dates you worked for the company, the number of work hours per week and annual salary plus benefits.
Good luck everybody