[1] J. Aczél: 
The general solution of two functional equations by reduction to functions additive in two variables and with the aid of Hamel bases. Glasnik Mat.-Fiz. Astr. 20 (1965), 65-72. 
MR 0198023 
[2] J. Aczél, Z. Daróczy: 
On Measures of Information and Their Characterizations. Academic Press, New York 1975. 
MR 0689178 
[3] B. R. Ebanks: 
Branching measures of information on strings. Canad. Math. Bull. 22 (1979), 433-448. 
MR 0563757 | 
Zbl 0434.94002 
[4] B. R. Ebanks: 
A characterization of separable utility functions. Kybernetika  17 (1981), 244-255. 
MR 0628212 | 
Zbl 0459.90005 
[5] J. Erdös: 
A remark on the paper 'On some functional equations' by S. Kurepa. Glasnik Mat.-Fiz. Astr. 14 (1959), 3-5. 
MR 0108660 | 
Zbl 0085.32903 
[6] M. Hosszú: 
On a functional equation treated by S. Kurepa. Glasnik Mat.-Fiz. Astr. 18 (1963), 59-60. 
MR 0165268 
[7] B. Jessen J. Karpfand A. Thorup: 
Some functional equations in groups and rings. Math. Scand. 22 (1968), 257-265. 
MR 0284739