wherever this keyword came from

doc/doc.bib

@@ -39,7 +39,7 @@
 	author = {Sugiyama, K. and Tagawa, S. and Toda, M.},
 	month = feb,
 	year = {1981},
-	keywords = {Computer displays, Constraint theory, Engineering drawings, Flowcharts, Hierarchical systems, Image recognition, Information science, Processor scheduling, Programming, Testing},
+	keywords = {Testing, Computer displays, Constraint theory, Engineering drawings, Flowcharts, Hierarchical systems, Image recognition, Information science, Processor scheduling, Programming},
 	pages = {109--125}
 }