diff --git a/doc/sequence.qbk b/doc/sequence.qbk
index 4625f8a5..6f50fe21 100644
--- a/doc/sequence.qbk
+++ b/doc/sequence.qbk
@@ -166,7 +166,7 @@ Bidirectional Sequence the following must be met:
     [[`__back__(s)`]        [Any type]                      []                      [Constant]]
     [[`__back__(s) = o`]    [Any type]                      [`s` is mutable and
                                                         `e = o`, where `e`
-                                                        is the first element
+                                                        is the last element
                                                         in the sequence, is
                                                         a valid expression.]    [Constant]]
 ]
@@ -237,14 +237,14 @@ any Random Access Sequence the following must be met:
     [[`__at_c__<N>(s)`]     [Any type]                      []                      [Constant]]
     [[`__at_c__<N>(s) = o`] [Any type]                      [`s` is mutable and
                                                         `e = o`, where `e`
-                                                        is the first element
-                                                        in the sequence, is
+                                                        is the N-th element from the beginning
+                                                        of the sequence, is
                                                         a valid expression.]        [Constant]]
     [[`__at__<M>(s)`]       [Any type]                      []                      [Constant]]
     [[`__at__<M>(s) = o`]   [Any type]                      [`s` is mutable and
                                                         `e = o`, where `e`
-                                                        is the first element
-                                                        in the sequence, is
+                                                        is the M-th element from the beginning
+                                                        of the sequence, is
                                                         a valid expression.]        [Constant]]
 ]
 
@@ -321,8 +321,7 @@ For any Associative Sequence the following expressions must be valid:
     [[`__at_key__<K>(s)`]       [Any type]                  []                      [Constant]]
     [[`__at_key__<K>(s) = o`]   [Any type]                  [`s` is mutable and
                                                         `e = o`, where `e`
-                                                        is the first element
-                                                        in the sequence, is
+                                                        is the element associated with K, is
                                                         a valid expression.]    [Constant]]
 ]
 
@@ -714,11 +713,11 @@ Returns the M-th element from the beginning of the sequence.
 [heading Synopsis]
 
     template <typename M, typename Sequence>
-    typename __result_of_at__<Sequence, N>::type
+    typename __result_of_at__<Sequence, M>::type
     at(Sequence& seq);
 
     template <typename M, typename Sequence>
-    typename __result_of_at__<Sequence const, N>::type
+    typename __result_of_at__<Sequence const, M>::type
     at(Sequence const& seq);
 
 [heading Parameters]