Hard and soft water : part 1 /
Ellis, D. R.
Hard and soft water : part 1 / David Rhodes Ellis. - Oxford : Pergamon, 1970. - A20, B20, [4] p. ; 11 x 17 cm. - Pergamon practical programme, 3 .
Water--Programmed instruction.
Hard and soft water : part 1 / David Rhodes Ellis. - Oxford : Pergamon, 1970. - A20, B20, [4] p. ; 11 x 17 cm. - Pergamon practical programme, 3 .
Water--Programmed instruction.
