Stubs for contributions, acknowledgements and back cover files

2017-10-12 18:02:51 +01:00 · 2017-10-12 18:02:51 +01:00 · 21070979dd
--- a/en/content/13contributions.md
+++ b/en/content/13contributions.md
--- a/en/content/14acknowledgements.md
+++ b/en/content/14acknowledgements.md
--- a/en/content/15back.md
+++ b/en/content/15back.md