Reference Letter / Could you please correct it for me

0Dear All,02br
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00I have been told that I can possibly be helped by you. I hope so. An employee has asked me for a reference letter (written in english) for an application for a Masters programme. As my first language is not English I am not confident with what I have written. Could you please correct the reference letter below for me.02br
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00Thank you very much,02br
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00Paul02br
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00Dear Sirs,02br
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00Miss Deborah Smith was employed as Quality and Environmental Consultant by this Company from March 1999 to December 2005.02br
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00She was responsible for supporting some of our clients, who were mainly manufacturers of construction materials such as ready mixed concrete and quarry aggregates. She developed and implemented with autonomy quality and environmental management systems according to ISO 9001 and 14001 standards in those clients.02br
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00Deborah made a substantial contribution to our company and proved to be an efficient, hard working, trustworthy and personable employee.02br
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00It is with great pleasure that I recommend Deborah for the programme she is applying for.02br
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00Yours sincerely0-