diff --git a/docs/source/getting_started/nanograv_15yr.rst b/docs/source/getting_started/nanograv_15yr.rst
index 8d1753d2..26832fbd 100644
--- a/docs/source/getting_started/nanograv_15yr.rst
+++ b/docs/source/getting_started/nanograv_15yr.rst
@@ -20,3 +20,7 @@ The initial set of **NANOGrav 15yr papers** are:
 
 The use of **holodeck in the 15yr astrophysics interpretation**:
 
+
+Errata
+======
+[1] : The 15yr Astro paper quotes an initial separation (the ``hard_sepa_init`` parameter) of "1e3 pc", this is incorrect and the actual value used in the analysis was 1e4 pc.  The values in the parameter-space objects (i.e. :py:class:`~holodeck.librarian.param_spaces_classic:_PS_Classic_Phenom`) is correct.
\ No newline at end of file
diff --git a/holodeck/librarian/param_spaces_classic.py b/holodeck/librarian/param_spaces_classic.py
index 6f49331a..38c96d08 100644
--- a/holodeck/librarian/param_spaces_classic.py
+++ b/holodeck/librarian/param_spaces_classic.py
@@ -1,4 +1,13 @@
 """'Classic' parameter spaces used in the NANOGrav 15yr analysis.
+
+15yr Astrophysics Analysis
+https://ui.adsabs.harvard.edu/abs/2023ApJ...952L..37A/abstract
+
+Notes
+-----
+[1] : The 15yr Astro paper quotes an initial separation (the `hard_sepa_init`) variable of "1e3 pc",
+      this is incorrect and the actual value used in the analysis was 1e4 pc.
+
 """
 
 from holodeck.constants import PC, GYR