hsmp documentation on work experience its URGENT

hi ,
My wife is aplying for HSMP as she is under 28 , i would like to know how to show her work experience , is it sufficient to give her job profile with start and end date of the jos on the company letter head signed by the director of the company . And how many reference do i need to give as she has been in just one job through out , only one reference of her director is enough . Or some other reference of her peer is also required .
Please also tell me other documents required in this regard ,like hairarchy of the comany , etc .
Please help .