--- a/src/SbpOperators/operators/standard_diagonal.toml	Wed Sep 22 13:09:17 2021 +0200
+++ b/src/SbpOperators/operators/standard_diagonal.toml	Wed Sep 22 13:09:46 2021 +0200
@@ -3,6 +3,20 @@
 description = "Standard operators for equidistant grids"
 type = "equidistant"
 cite = "A paper a long time ago in a galaxy far far away."
+# Review:
+# Suggested change:
+# "A paper a long time ago in a galaxy far far away." -->
+# "
+# Ken Mattsson, Jan Nordström,
+# Summation by parts operators for finite difference approximations of second derivatives,
+# Journal of Computational Physics,
+# Volume 199, Issue 2,
+# 2004,
+# Pages 503-540,
+# ISSN 0021-9991,
+# https://doi.org/10.1016/j.jcp.2004.03.001.
+# "
+# or perhaps a shorter version.
 
 [[stencil_set]]
 
@@ -30,6 +44,16 @@
 H.inner = "1"
 H.closure = ["17/48", "59/48", "43/48", "49/48"]
 
+# Review:
+# Add missing 4th order accurate D1 operator
+# D1.inner_stencil = ["1/12","-2/3","0","2/3","-1/12"]
+# D1.closure_stencils = [
+#     {s = [ "-24/17",  "59/34",  "-4/17", "-3/34",     "0",     "0"], c = 1},
+#     {s = [   "-1/2",      "0",    "1/2",     "0",     "0",     "0"], c = 2},
+#     {s = [   "4/43", "-59/86",      "0", "59/86", "-4/43",     "0"], c = 3},
+#     {s = [   "3/98",      "0", "-59/98",     "0", "32/49", "-4/49"], c = 4},
+# ]
+
 D2.inner_stencil = ["-1/12","4/3","-5/2","4/3","-1/12"]
 D2.closure_stencils = [
     {s = [     "2",    "-5",      "4",       "-1",     "0",     "0"], c = 1},