This file points to 4 pairs of files of the form    "?bx*"
("?" is a single-character wildcard and "*" is a multiple-character wildcard.)

Crossing File	Backbone Overlay
1bx4_A	1bx4_A_sse
1bx7	1bx7_sse
1bxd_A	1bxd_A_sse
1bxy_A	1bxy_A_sse