REFERENCES
- ANDERSON , J. H. , 1967 , Control Systems Centre Report No. 30 , U.M.I.S.T. , June ; 1968, Proc. Instn elect. Engrs (to be published); Ibid, (to be published) .
- ANDERSON , J. H. , and QUALTROUGH , G. H. , 1966 , Proc. Instn elect. Engrs , 113 , No. 10 : 1967, Control Systems Centre Report No. 10, June .
- CHIEN , K. L. , ERGIN , E. I. , LING , C. , and LEE , A. , 1958 , A.S.M.E. paper No.58-1RD-4 , April .
- KALMAN , R. E. , and KOEPKE , R. W. , 1958 , A.S.M.E. paper No. 58-IRD-6 , April .
- NICHOLSON , H. , 1964 , Proc. Instn elect. Engrs , 111 , No. 8 ; 1968. Ibid., 115, No. 6 .
- †communicated by Dr. A. G. J. McFarlane.