The "Dictionary" is based both on face-to-face interviews with 2,777 people carried out in 1,002 communities across the country between 1965 and 1970, and on a large collection of print and (recently) electronic materials, including diaries, letters, novels, histories, biographies, government documents, and newspapers. These sources are cited in individual entries to illustrate how the words have been used from the 17th century through the beginning of the 21st century. Entries may include pronunciations, variant forms, etymologies, and statements about regional and social distributions of words and forms.