removed supplemental notebooks about classes

Author: giumas

007_Dictionaries_and_Metadata.ipynb

@@ -134,36 +134,20 @@
     "By now, you may have noticed that the `str` variables in the above `chem_dict` are printed within single quotes `'` rather  than double quotes `\"`. This is an alternative and valid way to define strings in Python. However, mixing `'` and `\"` in the same string results in an error. For consistency, we always use `\"` here."
    ]
   },
-  {
-   "cell_type": "markdown",
-   "metadata": {},
-   "source": [
-    "## A `dict` is unordered"
-   ]
-  },
   {
    "cell_type": "markdown",
    "metadata": {},
    "source": [
     "When you print the content of a dictionary, you may have the items presented in an order that differs from the one that you used to populate the `dict`. This is **not** an error, but a specific property of a `dict`."
    ]
   },
-  {
-   "cell_type": "markdown",
-   "metadata": {},
-   "source": [
-    "<img align=\"left\" width=\"6%\" style=\"padding-right:10px;\" src=\"images/key.png\">\n",
-    "\n",
-    "A `dict` is an **unordered** container. The order of items insertion is not preserved."
-   ]
-  },
   {
    "cell_type": "markdown",
    "metadata": {},
    "source": [
     "<img align=\"left\" width=\"6%\" style=\"padding-right:10px;\" src=\"images/info.png\">\n",
     "\n",
-    "If you need to preserve the items order, Python provides a special dictionary called [`OrderedDict`](https://docs.python.org/3.6/library/collections.html?highlight=ordereddict#ordereddict-objects)."
+    "A `dict` is an **unordered** container. The order of items insertion is not preserved. If you need to preserve the items order, Python provides a special dictionary called [`OrderedDict`](https://docs.python.org/3.6/library/collections.html?highlight=ordereddict#ordereddict-objects)."
    ]
   },
   {

008_A_Class_as_a_Data_Container.ipynb

@@ -349,7 +349,7 @@
    "source": [
     "<img align=\"left\" width=\"6%\" style=\"padding-right:10px;\" src=\"images/info.png\">\n",
     "\n",
-    "If you are interested in learning more about classes, you may read [this supplemental notebook](SUP_First_Steps_of_a_Class.ipynb)."
+    "If you are interested in learning more about classes, you may want to explore the [Foundations of Ocean Data Science](https://www.hydroffice.org/manuals/epom/foundations_of_ocean_data_science.html) notebooks."
    ]
   },
   {
@@ -373,7 +373,8 @@
    "metadata": {},
    "source": [
     "* [The official Python 3.6 documentation](https://docs.python.org/3.6/index.html)\n",
-    "  * [Classes](https://docs.python.org/3.6/tutorial/classes.html)"
+    "  * [Classes](https://docs.python.org/3.6/tutorial/classes.html)\n",
+    "* [Foundations of Ocean Data Science](https://www.hydroffice.org/manuals/epom/foundations_of_ocean_data_science.html)"
    ]
   },
   {

009_Summing-Up.ipynb

@@ -258,7 +258,7 @@
     "\n",
     "We can check the success of this operation by printing depths and sound speed values. We will do this by accessing the values by index with the help of the [`range()`](https://docs.python.org/3.6/library/stdtypes.html?#range) type.\n",
     "\n",
-    "A `range()` with an integer value as single parameter represents a sequence of numbers ranging from 0 to the value passed as a parameter. In the code below, we use `range` with `10`:"
+    "A `range()` with an integer value as single parameter represents a sequence of numbers ranging from 0 up to (but not including) the value passed as a parameter. In the code below, we use `range` with `10`:"
    ]
   },
   {