WILLIAMS, K. W. (1970). Arithmetic: A semiprogrammed text. Prentice-Hall.
Chicago-čujuhus (17. p.)WILLIAMS, Keith W. Arithmetic: A Semiprogrammed Text. Englewood Cliffs, N.J: Prentice-Hall, 1970.
MLA-čujuhus (9. p.)WILLIAMS, Keith W. Arithmetic: A Semiprogrammed Text. Prentice-Hall, 1970.
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