Added the Arens extension.

refs.bib

@@ -268,4 +268,18 @@
   year      = {2002},
   isbn      = {978-1-85233-437-6},
   doi       = {10.1007/978-1-4471-3903-4}
-}
+}
+
+@article{ArensBilinear,
+ ISSN = {00029939, 10886826},
+ URL = {http://www.jstor.org/stable/2031695},
+ author = {Richard Arens},
+ journal = {Proceedings of the American Mathematical Society},
+ number = {6},
+ pages = {839--848},
+ publisher = {American Mathematical Society},
+ title = {The Adjoint of a Bilinear Operation},
+ urldate = {2026-08-13},
+ volume = {2},
+ year = {1951}
+}