diff --git a/doc/coroutine.qbk b/doc/coroutine.qbk
index a15b6d5..4ecf944 100644
--- a/doc/coroutine.qbk
+++ b/doc/coroutine.qbk
@@ -13,7 +13,7 @@ Implementations that produce sequences of values typically use asymmetric
 coroutines.
 [footnote Moura, Ana Lucia De and Ierusalimschy, Roberto.
 "Revisiting coroutines". ACM Trans. Program. Lang. Syst., Volume 31 Issue 2,
-February 2014, Article No. 6]
+February 2009, Article No. 6]
 
 
 [heading stackful]
diff --git a/doc/intro.qbk b/doc/intro.qbk
index 0714180..52d3a3e 100644
--- a/doc/intro.qbk
+++ b/doc/intro.qbk
@@ -54,7 +54,7 @@ function, such as traversal of binary trees (see example 'same fringe').
 [heading characteristics]
 Characteristics [footnote Moura, Ana Lucia De and Ierusalimschy, Roberto.
 "Revisiting coroutines". ACM Trans. Program. Lang. Syst., Volume 31 Issue 2,
-February 2014, Article No. 6] of a coroutine are:
+February 2009, Article No. 6] of a coroutine are:
 
 * values of local data persist between successive calls (context switches)
 * execution is suspended as control leaves coroutine and is resumed at certain time later