add url to DuCharme reference

1 files changed, 2 insertions, 0 deletions

diff --git a/ref.bib b/ref.bib
index c072d70..277159a 100644
--- a/ref.bib
+++ b/ref.bib
@@ -74,6 +74,8 @@
   subtitle =     "querying and updating with {SPARQL} 1.1",
   edition =      "2",
   date =         "2013-08-13",
+  URL =          "https://www.learningsparql.com/",
+  urldate =      "2024-05-06",
 }
 
 @Book{Ebersbach_2006,