Fixed the "them" typo caught by the sharp eye of
# layout
PyBIDS used to depend on [Grabbit](https://github.com/grabbles/grabbit) and here
-we described interactions with its Layout. Since them PyBIDS grew into an
+we described interactions with its Layout. Since then PyBIDS grew into an
independent beast and we refer the curious minds to
[our tutorial](../../examples/pybids_tutorial.ipynb) Jupyter notebook.
