[twenty-years] Fix missing commas in the bibliography

[Federico Mena Quintero <federico src gnome org>]

commit 538ab37aa4d17474a17fa9d4d71316229c7eba92
Author: Federico Mena Quintero <federico gnome org>
Date:   Tue Apr 28 20:47:57 2020 -0500

    Fix missing commas in the bibliography

 book/references.bib | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)
---
diff --git a/book/references.bib b/book/references.bib
index 6a01b84..9f8741e 100644
--- a/book/references.bib
+++ b/book/references.bib
@@ -43,9 +43,9 @@
 }
 
 @online {magcius-xplain,
-        author = {Jasper St. Pierre et al}
-        title  = {XPLAIN: Explaining X11 for the Rest of Us}
-        year   = {2017}
+        author = {Jasper St. Pierre et al},
+        title  = {XPLAIN: Explaining X11 for the Rest of Us},
+        year   = {2017},
         url    = {https://magcius.github.io/xplain/article/index.html}
 }
 
@@ -54,6 +54,6 @@
        title           = {Structure and Interpretation of Computer Programs, Second Edition},
        year            = {1996},
        publisher       = {MIT Press},
-       location        = {Cambridge, Massachusetts}
+       location        = {Cambridge, Massachusetts},
        url             = {https://mitpress.mit.edu/sicp/}
 }