[gegl] ops: add (citation) references to a couple more ops

[Øyvind Kolås <ok src gnome org>]

commit 1c71fe125ea1ca78f08c0448f7176a1d4d5fb7ec
Author: Øyvind Kolås <pippin gimp org>
Date:   Mon Apr 4 16:13:13 2016 +0200

    ops: add (citation) references to a couple more ops

 operations/common/bilateral-filter-fast.c |    4 ++--
 operations/common/bump-map.c              |    1 +
 2 files changed, 3 insertions(+), 2 deletions(-)
---
diff --git a/operations/common/bilateral-filter-fast.c b/operations/common/bilateral-filter-fast.c
index 34ec19e..165a909 100644
--- a/operations/common/bilateral-filter-fast.c
+++ b/operations/common/bilateral-filter-fast.c
@@ -494,8 +494,8 @@ gegl_op_class_init (GeglOpClass *klass)
   "name"       , "gegl:bilateral-filter-fast",
   "title"      , _("Bilateral Box Filter"),
   "categories" , "enhance:noise-reduction",
-  "description",
-           _("A fast approximation of bilateral filter, using a box-filter instead of a gaussian blur."),
+  "description", _("A fast approximation of bilateral filter, using a box-filter instead of a gaussian 
blur."),
+  "reference", "A Fast Approximation of the Bilateral Filter using a Signal Processing Approach Sylvain 
Paris and Frédo Durand European Conference on Computer Vision (ECCV'06)",
         NULL);
 }
 
diff --git a/operations/common/bump-map.c b/operations/common/bump-map.c
index 2f06053..ca14742 100644
--- a/operations/common/bump-map.c
+++ b/operations/common/bump-map.c
@@ -459,6 +459,7 @@ gegl_op_class_init (GeglOpClass *klass)
                      "It takes a buffer to be applied as a bump "
                      "map to another buffer and produces a nice embossing "
                      "effect."),
+    "reference", "'Fast Embossing Effects on Raster Image Data' in Graphics Gems IV (ISBN 0-12-336155-9).",
     NULL);
 }