Added links to doc pages

Author: jo-mueller

05_feature_extraction/04_feature_extraction.ipynb

@@ -48,7 +48,7 @@
     "\n",
     "*Remember*: Labelled images with multiple occurrences of the same type of objects (e.g., cells or nuclei) are the result of an *instance segmentation* task, whereas a unique label is assigned to every object.\n",
     "\n",
-    "Dictionaries in Python typically have a `key`-`value` structure and can be created and accessed like this:"
+    "[Dictionaries in Python](https://docs.python.org/3/tutorial/datastructures.html#dictionaries) typically have a `key`-`value` structure and can be created and accessed like this:"
    ]
   },
   {
@@ -123,7 +123,7 @@
    "id": "2461b674-5a27-4c94-960d-b3dc0fa3634d",
    "metadata": {},
    "source": [
-    "The `pandas` library provides a great amount of useful functions to work with tabular data. The pandas-equivalent of a dictionary is called a `DataFrame` and can be created from a dictionary by simple means:"
+    "The [Pandas](https://pandas.pydata.org/) library provides a great amount of useful functions to work with tabular data. The pandas-equivalent of a dictionary is called a `DataFrame` and can be created from a dictionary by simple means:"
    ]
   },
   {