diff --git a/COPYING.README b/COPYING.README
index 11af93ca7..52c077f81 100644
--- a/COPYING.README
+++ b/COPYING.README
@@ -2,5 +2,10 @@ Eigen is primarily MPL2 licensed. See COPYING.MPL2 and these links:
   http://www.mozilla.org/MPL/2.0/
   http://www.mozilla.org/MPL/2.0/FAQ.html
 
-Some files contain third-party code under BSD or other MPL2-compatible licenses,
-whence the other COPYING.* files here.
\ No newline at end of file
+Some files contain third-party code under BSD, LGPL, Apache, or other
+MPL2-compatible licenses, hence the other COPYING.* files here.
+
+Note that some optional external dependencies (e.g. FFTW, MPFR C++)
+and some bundled benchmark code (bench/btl/) are distributed under
+different licenses, including the GPL. Refer to the individual source
+files and their respective COPYING files for details.