link to left polar decomposition in the ClampUpAxes comments
diff --git a/magick/resample.c b/magick/resample.c
index 48070b3..5516c02 100644
--- a/magick/resample.c
+++ b/magick/resample.c
@@ -1334,10 +1334,17 @@
* of radius r in output space is an ellipse which contains, at
* least, a disc of radius r. (Make this hold for any r>0.)
*
- * METHOD: Find the singular values and (unit) left singular vectors
- * of Jinv, clampling up the singular values to 1, and multiplying
- * the unit left singular vectors by the new singular values in
- * order to get the minor and major ellipse axis vectors.
+ * SUMMARY OF THE METHOD: Compute the non-unitary factor of the left
+ * polar decomposition of the linear transformation defining the
+ * ellipse and make sure that both its columns have norm at least 1.
+ * Because rotations and reflexions map disks to themselves, it is
+ * not necessary to compute the other factor of the polar
+ * decomposition.
+ *
+ * DETAILS: Find the singular values and (unit) left singular
+ * vectors of Jinv, clampling up the singular values to 1, and
+ * multiplying the unit left singular vectors by the new singular
+ * values in order to get the minor and major ellipse axis vectors.
*
* Inputs:
*