Orttung, William Herbert.
Chemistry unit / William Herbert Orttung. - Chicago : Encyclopaedia Britannica Educational Corporation, 1964. - [8], 113 p. : ill. ; 27 cm. - TEMAC programmed learning materials ; General science series .
Chemistry --Programmed instruction.
540 / ORC
Chemistry unit / William Herbert Orttung. - Chicago : Encyclopaedia Britannica Educational Corporation, 1964. - [8], 113 p. : ill. ; 27 cm. - TEMAC programmed learning materials ; General science series .
Chemistry --Programmed instruction.
540 / ORC