// Move reference to ReadiumSDK to top.
function setReadiumSDK() {
  window.ReadiumSDK = document.getElementById("ucimte_iucbenik_html").contentWindow.ReadiumSDK;
  
  if (window.ReadiumSDK == null || typeof window.ReadiumSDK === "undefined" || window.ReadiumSDK.reader == null || typeof window.ReadiumSDK.reader === "undefined") {
    setTimeout(setReadiumSDK, 500);
  }
}
setReadiumSDK();