function openConcept(evt, ConceptName) {
  var i, x, tablinks;
  x = document.getElementsByClassName("concept");
  for (i = 0; i < x.length; i++) {
    x[i].style.display = "none";
  }
  tablinks = document.getElementsByClassName("tablink");
  for (i = 0; i < x.length; i++) {
    tablinks[i].className = tablinks[i].className.replace(" w3-border-red", "");
  }
  document.getElementById(ConceptName).style.display = "block";
  evt.currentTarget.firstElementChild.className += " w3-border-red";
}

function Dropdown(id) {
  var x = document.getElementById(id);
  if (x.className.indexOf("w3-show") == -1) {
    x.className += " w3-show";
  } else {
    x.className = x.className.replace(" w3-show", "");
  }
}