Link up some stuff in the vectors chapter

src/doc/trpl/vectors.md

@@ -1,13 +1,18 @@
 % Vectors
 
 A *vector* is a dynamic or "growable" array, implemented as the standard
-library type [`Vec<T>`](../std/vec/) (Where `<T>` is a [Generic](./generics.md) statement). Vectors always allocate their data on the heap. Vectors are to slices
-what `String` is to `&str`. You can create them with the `vec!` macro:
+library type [`Vec<T>`](../std/vec/) (Where `<T>` is a [Generic](./generics.md)
+statement). Vectors always allocate their data on the heap. Vectors are to
+[slices][slices] what [`String`][string] is to `&str`. You can
+create them with the `vec!` macro:
 
 ```{rust}
 let v = vec![1, 2, 3]; // v: Vec<i32>
 ```
 
+[slices]: primitive-types.html#slices
+[string]: strings.html
+
 (Notice that unlike the `println!` macro we've used in the past, we use square
 brackets `[]` with `vec!`. Rust allows you to use either in either situation,
 this is just convention.)