1. D. F. Dawson, Variation properties of sequences,Mat. Vesnik 6 (1969), 436–441.MR 41: 2252
2. I. B. Lacković andM. R. Jovanović, On a class of real sequences which satisfy a difference inequality,Univ. Beograd. Publ. Elektrotehn. Fak. Ser. Mat. Fiz. no. 678–715 (1980), 99–104.MR 83b: 40004
3. I. B. Lacković andLj. M. Kocić, On a linear difference operator,Univ. Beograd. Publ. Elektrotehn. Fak. Ser. Mat. Fiz. no. 634–677 (1979), 203–207.MR 81f: 39001
4. I. B. Lacković andLj. M. Kocić, On some linear transformations of quasi-monotone sequences,Univ. Beograd. Publ. Elektrotehn. Fak. Ser. Mat. Fiz. no 634–677 (1979), 208–213.MR 81j: 40003
5. I. B. Lacković andLj. M. Kocić, Invariant transformations of some sequence classes,Univ. Beograd. Publ. Elektrotehn. Fak. Ser. Mat. Fiz. no. 678–715 (1980), 117–126.MR 82g: 26025