The Delphi technique consists of three or four rounds of questionnaires mailed to a panel of experts. Strengths of the Delphi are its combination of qualitative (written) and quantitative (numerical) data and its ability to form a consensus of expert opinion. Limitations are time involved for mailing and receiving replies and lack of stimulation from face-to-face contact.
Julia A. Gamon (Sun,) studied this question.