Join problem: throwing error, join extra operand

I want to join 3 files on a column which has sorted unique numeric values (those files have only one column of values though) and starts with same prefix for an example "usi". Now, while I am doing this join -j 1 ../Test_Data/usi* > ../Test_Data/join_output.txt I am finding following error: > join: extra operand `usi_rtree_lw_100000.txt' > Try `join --help' for more information. Any ideas?