diff --git a/src/mdevaluate/coordinates.py b/src/mdevaluate/coordinates.py
index 5fc576a..9bf5f88 100755
--- a/src/mdevaluate/coordinates.py
+++ b/src/mdevaluate/coordinates.py
@@ -565,7 +565,6 @@ def normal_vectors(
     vec = np.cross(vectors_a, vectors_b)
     if normed:
         vec /= np.linalg.norm(vec, axis=-1).reshape(-1, 1)
-    vec.reference = coords_a
     return vec
 
 
diff --git a/src/mdevaluate/pbc.py b/src/mdevaluate/pbc.py
index 66c903b..f57a60d 100644
--- a/src/mdevaluate/pbc.py
+++ b/src/mdevaluate/pbc.py
@@ -8,20 +8,6 @@ from itertools import product
 from .logging import logger
 
 
-def pbc_diff_old(v1, v2, box):
-    """
-    Calculate the difference of two vestors, considering optional boundary conditions.
-    """
-    if box is None:
-        v = v1 - v2
-    else:
-        v = v1 % box - v2 % box
-        v -= (v > box / 2) * box
-        v += (v < -box / 2) * box
-
-    return v
-
-
 def pbc_diff(v1, v2=None, box=None):
     if box is None:
         out = v1 - v2