  var menu = [ 
	      "index.html", 
	      "kap1.html", 
	      "kap1-1.html", 
	      "kap1-2.html", 
	      "kap1-3.html", 
	      "kap1-4.html", 
	      "kap2.html", 
	      "kap3.html", 
	      "kap3-1.html", 
	      "kap3-2.html", 
	      "kap3-3.html", 
	      "kap4.html", 
	      "kap4-1.html", 
	      "kap4-2.html", 
	      "kap5.html", 
	      "kap6.html", 
	      "kap6-1.html", 
	      "kap6-2.html", 
	      "kap6-3.html", 
	      "kap6-4.html", 
	      "exercises.html", 
	      "exercise1.html", 
	      "exercise2.html", 
	      "exercise3.html", 
	      "exercise4.html", 
	      "exercise5.html", 
	      "exercise6.html", 
	      "exercise7.html", 
	      "exercise8.html", 
	      "exercise9.html", 
	      "exercise10.html", 
	      "exercise11.html", 
	      "exercise12.html", 
	      "exercise13.html", 
	      "exercise14.html", 
	      "exercise15.html", 
	      "appendix.html", 
	      "app-lit.html", 
	      "app-matlab.html", 
	      "bild26_m.html", 
	      "bild28_m.html", 
	      "computeEigenvalues_m.html", 
	      "createDemoTruss_m.html", 
	      "createEnvelope_m.html", 
	      "createMatrices_m.html", 
	      "createSineWave_m.html", 
	      "demofunc4_m.html", 
	      "erzwungen_m.html", 
	      "erzwungenp_m.html", 
	      "getNumber_m.html", 
	      "glocke_m.html", 
	      "loadTruss1_m.html", 
	      "loadTruss_m.html", 
	      "matschwing2d_m.html", 
	      "plotModeAnimation_m.html", 
	      "plotMode_m.html", 
	      "plotTruss1_m.html", 
	      "plotTruss_m.html", 
	      "radioaktiv_m.html", 
	      "radiokette_m.html", 
	      "saveTruss1_m.html", 
	      "saveTruss_m.html", 
	      "schwing2d_m.html", 
	      "schwingNd_m.html", 
	      "solveVibrationODE_m.html", 
	      "spektrum_m.html", 
	      "trapez1_m.html", 
	      "trapez2_m.html", 
	      "trapez_m.html", 
	      "trussGUI1_m.html", 
	      "trussGUI2_m.html", 
	      "trussGUI_m.html", 
	      "zeichneFunktion_m.html",
	      "app-daten.html"
              ];

  var pageindex;

  function initIndex() {
    myname = window.location.href;
    for (i=0; i < menu.length; i++) {
      if (myname.indexOf(menu[i]) != -1) {
	pageindex = i;
	return;
      }
    }
  }

  function setIndex(i) {
    pageindex = i;
    displayit();
  }

  function increment() {
    if (pageindex < menu.length - 1) {
      pageindex++;
    }
    displayit();
  }

  function decrement() {
    if (pageindex > 0) {
      pageindex--;
    }
    displayit();
  }

  function displayit() {
    window.location.href = menu[pageindex];
  }

