Hello,
Record of employment u can request from Service Canada. It will show all your previous Employers -http://www.servicecanada.gc.ca/fi-if/index.jsp?app=prfl&frm=ins3166
Letter of employment - Contact individual employers and ask them to provide a official letter from HR. Letter should be on company letter paper (have a header), address, have your name, start date, finish date, # of hours worked, salary, job title, task descriptions.
If you have questions let me know
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Anton