The most effective letters of recommendation are written by professors or work supervisors who know you well enough to describe your academic, personal, or professional achievements and potential with candor, detail, and objectivity. Letters that compare you to your academic peers are often the most useful. Most schools do not consider general, unreservedly praiseworthy letters helpful.
References may also be required of companies seeking to win contracts, particularly in the fields of engineering, consultancy, industry and construction, and with regard to public procurement and tenders. Reference letters for organizations are used to assess its ability to deliver the required level of service.