I'd like to do following thing. In my text I want to refer to citations with
and in the reference section under this reference, e.g.  there should be sth. as follows:
 (a) author1, author2, ..., journal1, vol1, pp1 year1, (b) author3, author4, ..., journal2, vol2, pp2, year2 (c) and so on
It is not the question about the style of the reference, but how to make many references (a), (b), (c) under one citation ?