Index/Match cross search and extract

hi guys i need a little help, ill try and explain my situation as best i can

sheet 2
column C is list of chemicals (to give context)
column A is a list of the publication numbers they apear in
column B is GOING to be the list of publication titles they are in

sheet 3
column A is a complete list of every publication number in our library
column B is the corresponding publication title

what i would like to do is extract the title from sheet 3 and input it into column B sheet 2 corresponding to whatever pub number is listed in column A of sheet 2

the code i have so far is in column b sheet 2 "=INDEX(Sheet3!B:B,MATCH(A2,Sheet3!A:A,0))"

now the problem i have is this works perfectly when only one pub is listed in a cell in column A sheet 2 but when there is more than one pub listed (ie "pub number" next line in cell "another pub number") it gives a N/A result.

is there anyway to call up multiple pub titles from the multiple pub numbers within one cell

cheers for all your help