Update links to external crates
diff --git a/src/parse_quote.rs b/src/parse_quote.rs
index 0c70b08..07320e2 100644
--- a/src/parse_quote.rs
+++ b/src/parse_quote.rs
@@ -1,7 +1,7 @@
/// Quasi-quotation macro that accepts input like the [`quote!`] macro but uses
/// type inference to figure out a return type for those tokens.
///
-/// [`quote!`]: https://docs.rs/quote/0.4/quote/index.html
+/// [`quote!`]: https://docs.rs/quote/0.6/quote/index.html
///
/// The return type can be any syntax tree node that implements the [`Synom`]
/// trait.
diff --git a/src/spanned.rs b/src/spanned.rs
index 6e2215d..80cf6aa 100644
--- a/src/spanned.rs
+++ b/src/spanned.rs
@@ -88,7 +88,7 @@
/// [`ToTokens`] from the `quote` crate. It is sealed and cannot be implemented
/// outside of the Syn crate other than by implementing `ToTokens`.
///
-/// [`ToTokens`]: https://docs.rs/quote/0.4/quote/trait.ToTokens.html
+/// [`ToTokens`]: https://docs.rs/quote/0.6/quote/trait.ToTokens.html
///
/// See the [module documentation] for an example.
///
@@ -100,7 +100,7 @@
/// Returns a `Span` covering the complete contents of this syntax tree
/// node, or [`Span::call_site()`] if this node is empty.
///
- /// [`Span::call_site()`]: https://docs.rs/proc-macro2/0.2/proc_macro2/struct.Span.html#method.call_site
+ /// [`Span::call_site()`]: https://docs.rs/proc-macro2/0.4/proc_macro2/struct.Span.html#method.call_site
fn span(&self) -> Span;
}