diff --git a/besskge/dataset.py b/besskge/dataset.py
index 17a12d1..a142238 100644
--- a/besskge/dataset.py
+++ b/besskge/dataset.py
@@ -137,7 +137,7 @@ def from_dataframe(
         head_column: Union[int, str],
         relation_column: Union[int, str],
         tail_column: Union[int, str],
-        entity_types: Optional[Union["pd.Series[str]", Dict[str, str]]] = None,
+        entity_types: Optional[Union[pd.Series, Dict[str, str]]] = None,  # type: ignore
         split: Tuple[float, float, float] = (0.7, 0.15, 0.15),
         seed: int = 1234,
     ) -> "KGDataset":
@@ -157,7 +157,7 @@ def from_dataframe(
             Name of the DataFrame column storing tail entities
         :param entity_types:
             If entities have types, dictionary or pandas Series of mappings
-            entity label -> entity type.
+            entity label -> entity type (as strings).
         :param split:
             Tuple to set the train/validation/test split.
             Only used if no pre-defined dataset split is specified,
diff --git a/docs/source/conf.py b/docs/source/conf.py
index e77438b..6369378 100644
--- a/docs/source/conf.py
+++ b/docs/source/conf.py
@@ -62,6 +62,7 @@
 intersphinx_mapping = {
     "python": ("https://docs.python.org/3", None),
     "numpy": ("https://numpy.org/doc/stable", None),
+    "pandas": ("http://pandas.pydata.org/pandas-docs/dev", None),
     "torch": ("https://pytorch.org/docs/stable", None),
     "rtd": ("https://docs.readthedocs.io/en/stable/", None),
     "sphinx": ("https://www.sphinx-doc.org/en/master/", None),