var chapter_list = new Array(
  ["Vol.01 Ch.001","v01/c001"],
  ["Vol.01 Ch.001.1","v01/c001.1"],
  ["Vol.01 Ch.002","v01/c002"],
  ["Vol.01 Ch.003","v01/c003"],
  ["Vol.01 Ch.004","v01/c004"],
  ["Vol.02 Ch.005","v02/c005"],
  ["Vol.02 Ch.006","v02/c006"],
  ["Vol.02 Ch.007","v02/c007"],
  ["Vol.02 Ch.008","v02/c008"],
  ["Vol.03 Ch.009: [includes chapters 9 & 10]","v03/c009"],
  ["Vol.03 Ch.011: [includes chapters 11 & 12]","v03/c011"],
  ["Vol.03 Ch.012","v03/c012"],
  ["Vol.04 Ch.013: [includes chapters 13, 14, & 15]","v04/c013"],
  ["Vol.04 Ch.016: [includes chapter 16]","v04/c016"],
  ["Vol.05 Ch.017: [includes chapters 17, 18, & 19]","v05/c017"],
  ["Vol.05 Ch.020: [includes chapter 20]","v05/c020"],
  ["Vol.06 Ch.021","v06/c021"],
  ["Vol.06 Ch.022","v06/c022"],
  ["Vol.06 Ch.023","v06/c023"],
  ["Vol.06 Ch.024","v06/c024"],
  ["Vol.07 Ch.025","v07/c025"],
  ["Vol.07 Ch.026","v07/c026"],
  ["Vol.07 Ch.027","v07/c027"],
  ["Vol.07 Ch.028","v07/c028"],
  ["Vol.08 Ch.029","v08/c029"],
  ["Vol.08 Ch.030","v08/c030"],
  ["Vol.08 Ch.031","v08/c031"],
  ["Vol.08 Ch.032","v08/c032"],
  ["Vol.09 Ch.033","v09/c033"],
  ["Vol.09 Ch.034","v09/c034"],
  ["Vol.09 Ch.035","v09/c035"],
  ["Vol.09 Ch.036","v09/c036"],
  ["Vol.10 Ch.037","v10/c037"],
  ["Vol.10 Ch.038","v10/c038"],
  ["Vol.10 Ch.039","v10/c039"]
);

var total_chapters = 35;

for (var i = 0; i < chapter_list.length; i++) {
  document.getElementById('top_chapter_list').options[i] = new Option(chapter_list[i][0], chapter_list[i][1]);
  document.getElementById('bottom_chapter_list').options[i] = new Option(chapter_list[i][0], chapter_list[i][1]);
}
document.getElementById('top_chapter_list').value=current_chapter;
document.getElementById('bottom_chapter_list').value=current_chapter;
var current_chapter_index = document.getElementById('top_chapter_list').selectedIndex;