proofread existing changes.

Author: BillWagner

standard/classes.md

@@ -2757,7 +2757,7 @@ A compile-time error occurs unless all of the following are true for an override
 - The overridden base method is a virtual, abstract, or override method. In other words, the overridden base method cannot be static or non-virtual.
 - The overridden base method is not a sealed method.
 - The override method has a return type that is convertible by an identity conversion or (if the method has a value return) an implicit reference conversion to the return type of the overridden base method.
-- The override method has a return type that is convertible by an identity conversion or (if the method has a value return a) an implicit reference conversion to the return type of every override of the overridden base method that is declared in a (direct or indirect) base type of the override method.
+- The override method has a return type that is convertible by an identity conversion or (if the method has a value return) an implicit reference conversion to the return type of every override of the overridden base method that is declared in a (direct or indirect) base type of the override method.
 - The override declaration and the overridden base method have the same declared accessibility. In other words, an override declaration cannot change the accessibility of the virtual method. However, if the overridden base method is protected internal and it is declared in a different assembly than the assembly containing the override declaration then the override declaration’s declared accessibility shall be protected.
 - The override method's return type is at least as accessible as the override method.
   > *Note*: This constraint permits an override method in a `private` class to have a `private` return type.  However, it requires a `public` override method in a `public` type to have a `public` return type. *end note*

standard/interfaces.md

@@ -1099,7 +1099,7 @@ Members of a constructed interface type are considered to have any type paramete
 
 For purposes of interface mapping, a class, interface, or struct member `A` matches an interface member `B` when:
 
-- `A` and `B` are methods, and the name, type, and parameter lists of `A` and `B` are identical, and the return type of `A` is convertible to the return type of `B` via an identity of implicit reference conversion to the return type of `B`.
+- `A` and `B` are methods, and the name, type, and parameter lists of `A` and `B` are identical, and the return type of `A` is convertible to the return type of `B` via an identity or implicit reference conversion.
 - `A` and `B` are properties, the name of `A` and `B` are identical, `A` has the same accessors as `B` (`A` is permitted to have additional accessors if it is not an explicit interface member implementation), and the type of `A` is convertible to the return type of `B` via an identity conversion or, if `A` is a readonly property, an implicit reference conversion.
 - `A` and `B` are events, and the name and type of `A` and `B` are identical.
 - `A` and `B` are indexers, the parameter lists of `A` and `B` are identical, `A` has the same accessors as `B` (`A` is permitted to have additional accessors if it is not an explicit interface member implementation), and the type of `A` is convertible to the return type of `B` via an identity conversion or, if `A` is a readonly indexer, an implicit reference conversion.