diff --git a/README.md b/README.md
index c3005c4..3aaf8b8 100644
--- a/README.md
+++ b/README.md
@@ -27,27 +27,8 @@ Feature                            | Supported? | Description
 [**1. Views**][cg-views]           |            |
 owner                              | ☑   | an alias for a raw pointer
 not_null                           | ☑   | restricts a pointer / smart pointer to hold non-null values
-strict_not_null                    | ☑   | a stricter version of `not_null` with explicit constructors
 span                               | ☑   | a view over a contiguous sequence of memory. Based on the standardized verison of `std::span`, however `gsl::span` enforces bounds checking. See the [wiki](https://github.com/microsoft/GSL/wiki/gsl::span-and-std::span) for additional information.
 span_p                             | ☐   | spans a range starting from a pointer to the first place for which the predicate is true
-basic_zstring                      | ☑   | a pointer to a C-string (zero-terminated array) with a templated char type
-zstring                            | ☑   | an alias to `basic_zstring` with a char type of char
-czstring                           | ☑   | an alias to `basic_zstring` with a char type of const char
-wzstring                           | ☑   | an alias to `basic_zstring` with a char type of wchar_t
-cwzstring                          | ☑   | an alias to `basic_zstring` with a char type of const wchar_t
-u16zstring                         | ☑   | an alias to `basic_zstring` with a char type of char16_t
-cu16zstring                        | ☑   | an alias to `basic_zstring` with a char type of const char16_t
-u32zstring                         | ☑   | an alias to `basic_zstring` with a char type of char32_t
-cu32zstring                        | ☑   | an alias to `basic_zstring` with a char type of const char32_t
-basic_string_span                  | ☑   | like `span` but for strings with a templated char type
-string_span                        | ☑   | an alias to `basic_string_span` with a char type of char
-cstring_span                       | ☑   | an alias to `basic_string_span` with a char type of const char
-wstring_span                       | ☑   | an alias to `basic_string_span` with a char type of wchar_t
-cwstring_span                      | ☑   | an alias to `basic_string_span` with a char type of const wchar_t
-u16string_span                     | ☑   | an alias to `basic_string_span` with a char type of char16_t
-cu16string_span                    | ☑   | an alias to `basic_string_span` with a char type of const char16_t
-u32string_span                     | ☑   | an alias to `basic_string_span` with a char type of char32_t
-cu32string_span                    | ☑   | an alias to `basic_string_span` with a char type of const char32_t
 [**2. Owners**][cg-owners]         |            |
 unique_ptr                         | ☑   | an alias to `std::unique_ptr`
 shared_ptr                         | ☑   | an alias to `std::shared_ptr`
@@ -70,11 +51,30 @@ narrow_cast                        | ☑   | a narrowing cast for values an
 narrowing_error                    | ☑   | a custom exception type thrown by `narrow()`
 [**5. Concepts**][cg-concepts]     | ☐   |
 
-## The following features do not exist in C++ Core Guidelines:
+## The following features do not exist in or have been removed from the C++ Core Guidelines:
 Feature                            | Supported? | Description
 -----------------------------------|:----------:|-------------
-multi_span                         | ☐   | Deprecated. Support for this type has been discontinued.
+strict_not_null                    | ☑   | A stricter version of `not_null` with explicit constructors
+multi_span                         | ☐   | Deprecated. Multi-dimensional span.
 strided_span                       | ☐   | Deprecated. Support for this type has been discontinued.
+basic_zstring                      | ☐   | Deprecated. A pointer to a C-string (zero-terminated array) with a templated char type
+zstring                            | ☐   | Deprecated. An alias to `basic_zstring` with a char type of char
+czstring                           | ☐   | Deprecated. An alias to `basic_zstring` with a char type of const char
+wzstring                           | ☐   | Deprecated. An alias to `basic_zstring` with a char type of wchar_t
+cwzstring                          | ☐   | Deprecated. An alias to `basic_zstring` with a char type of const wchar_t
+u16zstring                         | ☐   | Deprecated. An alias to `basic_zstring` with a char type of char16_t
+cu16zstring                        | ☐   | Deprecated. An alias to `basic_zstring` with a char type of const char16_t
+u32zstring                         | ☐   | Deprecated. An alias to `basic_zstring` with a char type of char32_t
+cu32zstring                        | ☐   | Deprecated. An alias to `basic_zstring` with a char type of const char32_t
+basic_string_span                  | ☐   | Deprecated. Like `span` but for strings with a templated char type
+string_span                        | ☐   | Deprecated. An alias to `basic_string_span` with a char type of char
+cstring_span                       | ☐   | Deprecated. An alias to `basic_string_span` with a char type of const char
+wstring_span                       | ☐   | Deprecated. An alias to `basic_string_span` with a char type of wchar_t
+cwstring_span                      | ☐   | Deprecated. An alias to `basic_string_span` with a char type of const wchar_t
+u16string_span                     | ☐   | Deprecated. An alias to `basic_string_span` with a char type of char16_t
+cu16string_span                    | ☐   | Deprecated. An alias to `basic_string_span` with a char type of const char16_t
+u32string_span                     | ☐   | Deprecated. An alias to `basic_string_span` with a char type of char32_t
+cu32string_span                    | ☐   | Deprecated. An alias to `basic_string_span` with a char type of const char32_t
 
 This is based on [CppCoreGuidelines semi-specification](https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#gsl-guidelines-support-library).