diff --git a/3 - Images and Text.ipynb b/3 - Images and Text.ipynb
index 0d9db2736e96643e37629af3dfdce7aec3a0a851..8e2895f63b7da5356c695370782eda7bbd4c4345 100644
--- a/3 - Images and Text.ipynb	
+++ b/3 - Images and Text.ipynb	
@@ -205,35 +205,30 @@
     }
    },
    "source": [
-    "* The ONB Labs viewers use IIIF: [https://labs.onb.ac.at/en/dataset/akon/](https://labs.onb.ac.at/en/dataset/akon/)\n",
-    "\n",
-    "**TODO**: Available viewers, available data sources (europeana, ?), applications"
+    "* The ONB Labs viewers use IIIF: [https://labs.onb.ac.at/en/dataset/akon/](https://labs.onb.ac.at/en/dataset/akon/)\n"
    ]
   },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "metadata": {},
-   "outputs": [],
-   "source": []
-  },
   {
    "cell_type": "markdown",
    "metadata": {
     "slideshow": {
-     "slide_type": "subslide"
+     "slide_type": "fragment"
     }
    },
-   "source": []
+   "source": [
+    "* Awesome IIIF-related resources : [https://github.com/IIIF/awesome-iiif](https://github.com/IIIF/awesome-iiif)"
+   ]
   },
   {
    "cell_type": "markdown",
    "metadata": {
     "slideshow": {
-     "slide_type": "subslide"
+     "slide_type": "fragment"
     }
    },
-   "source": []
+   "source": [
+    "* [https://showcase.iiif.io/](https://showcase.iiif.io/)"
+   ]
   },
   {
    "cell_type": "markdown",
@@ -269,6 +264,75 @@
     "    "
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {
+    "slideshow": {
+     "slide_type": "slide"
+    }
+   },
+   "source": [
+    "## Overview OCR formats"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {
+    "slideshow": {
+     "slide_type": "subslide"
+    }
+   },
+   "source": [
+    "* ALTO (Analyzed Layout and Text Object)\n",
+    "    * OCR (Optical Character Recognition) data representation format\n",
+    "    * XML Schema\n",
+    "    * [https://github.com/altoxml](https://github.com/altoxml)\n",
+    "    * [https://www.loc.gov/standards/alto/](https://www.loc.gov/standards/alto/)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {
+    "slideshow": {
+     "slide_type": "subslide"
+    }
+   },
+   "source": [
+    "* 3 ALTO main elements\n",
+    "    * `<Description>`\n",
+    "        *  metadata and general settings (e.g. measurement units) about the ALTO file\n",
+    "    * `<Styles>`\n",
+    "        *  text and paragraph styles\n",
+    "    * `<Layout>`\n",
+    "        * content information\n",
+    "        * subdivided into `<Page>` elements"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {
+    "slideshow": {
+     "slide_type": "subslide"
+    }
+   },
+   "source": [
+    "![ALTO page element](./media/alto.png)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {
+    "slideshow": {
+     "slide_type": "subslide"
+    }
+   },
+   "source": [
+    "* hOCR\n",
+    "    * alternative to ALTO\n",
+    "    * based on XHTML\n",
+    "    * not used in the ONB Labs"
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": null,
@@ -294,7 +358,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.7.3"
+   "version": "3.6.7"
   }
  },
  "nbformat": 4,
diff --git a/media/alto.png b/media/alto.png
new file mode 100644
index 0000000000000000000000000000000000000000..12480d2f78bb4bf2a3e89719786d8c36b6121abc
Binary files /dev/null and b/media/alto.png differ