Added mutually recursive records example to records documentation

docs/fsharp/language-reference/records.md

@@ -84,6 +84,29 @@ let defaultRecord2 = { Field1 = 1; Field2 = 25 }
 let rr3 = { defaultRecord1 with Field2 = 42 }
 ```
 
+## Creating Mutually Recursive Records
+
+Sometime when creating a record, you may want to have it depend on another type that you would like to define afterwards. This is a compile error unless you define the record types to be mutually recursive.
+
+Defining mutually recursive records is done with the `and` keyword. This lets you link 2 or more record types together.
+
+For example, the following code defines a `Person` and `Address` type as mutually recursive:
+
+```fsharp
+// Create a Person type and use the Address type that is not defined
+type Person =
+  { Name: string
+    Age: int
+    Address: Address }
+// Define the Address type which is used in the Person record
+and Address =
+  { Line1: string
+    Line2: string
+    PostCode: string }
+```
+
+If you were to define the previous example without the `and` keyword, then it would not compile. The `and` keyword is required for mutually recursive definitions.
+
 ## Pattern Matching with Records
 
 Records can be used with pattern matching. You can specify some fields explicitly and provide variables for other fields that will be assigned when a match occurs. The following code example illustrates this.
@@ -122,4 +145,4 @@ If you need reference equality for records, add the attribute `[<ReferenceEquali
 - [Classes](classes.md)
 - [F# Language Reference](index.md)
 - [Reference-Equality](https://msdn.microsoft.com/visualfsharpdocs/conceptual/core.referenceequalityattribute-class-%5bfsharp%5d)
-- [Pattern Matching](pattern-matching.md)
+- [Pattern Matching](pattern-matching.md)