between two things
among many (more than two)

В тупик заводит предложение типа

договор заключенный между А, Б и В

contract concluded "between" or "among" A, B and C

Despite the rule I would use "between".

Any ideas?

they quarrelled among themselves

Between
A space which separates. Strictly applicable only with reference to two things, but this may be understood as including cases in which a number of things are discriminated collectively as two wholes, or as taken in pairs, or where one thing is set off against a number of others. In re McShane's Will, 158 Misc. 777, 286 N.Y.S. 680, 682. Sometimes used synonymously with "among". In re Moore's Estate, 157 Pa.Super. 296, 43 A.2d 359. As a measure or indication of distance, this word has the effect of excluding the two termini. If an act is to be done "between" two certain days, it must be performed before the commencement of the latter day. In computing the time in such a case, both the days named are to be excluded.

Consult with: http://www.multitran.ru/Download/Technical_Style_Guide.zip