Fix refs.bib entry

common/refs.bib

@@ -1,4 +1,5 @@
 % Use <AUTHOR>:<YEAR>:<TOPIC> for the reference labels.
+% Use the surname of the main author for AUTHOR.
 % Sort lexicographically by (YEAR, AUTHOR, TOPIC).
 @article{Liu:1973:Scheduling,
   author      = {Liu, C. L. and Layland, James W.},
@@ -29,7 +30,7 @@
   year        = {1990},
   pages       = {201-209},
 }
-@article{Lui:1990:Ada,
+@article{Sha:1990:Ada,
   author      = {Sha, Lui and Goodenough, J. B.},
   journal     = {Computer},
   title       = {{Real-time scheduling theory and Ada}},