diff --git a/ascii.cabal b/ascii.cabal
--- a/ascii.cabal
+++ b/ascii.cabal
@@ -1,7 +1,7 @@
 cabal-version: 3.0
 
 name: ascii
-version: 1.3.1.0
+version: 1.4.0.0
 synopsis: The ASCII character set and encoding
 category: Data, Text
 
@@ -26,75 +26,50 @@
 common base
     default-language: Haskell2010
     ghc-options: -Wall
-
-    default-extensions:
-        NoImplicitPrelude
-
+    default-extensions: NoImplicitPrelude
     build-depends:
-        base ^>= 4.14 || ^>= 4.15 || ^>= 4.16 || ^>= 4.17
+        ascii-caseless == 0.0.0.*
+      , ascii-char == 1.0.0.*
+      , ascii-group == 1.0.0.*
+      , ascii-case == 1.0.1.*
+      , ascii-numbers == 1.1.0.*
+      , ascii-predicates == 1.0.1.*
+      , ascii-superset == 1.2.0.*
+      , ascii-th == 1.1.1.*
+      , base ^>= 4.14 || ^>= 4.15 || ^>= 4.16 || ^>= 4.17
+      , bytestring ^>= 0.10.12 || ^>= 0.11
       , text ^>= 1.2.4 || ^>= 2.0
 
 library
     import: base
     hs-source-dirs: library
-
-    build-depends:
-        bytestring ^>= 0.10.12 || ^>= 0.11
-
+    default-extensions: RankNTypes ScopedTypeVariables TypeApplications
     exposed-modules: ASCII
-
-    build-depends: ascii-caseless == 0.0.0.*
     reexported-modules:
-        ASCII.Caseless
-
-    build-depends: ascii-char == 1.0.0.*
-    reexported-modules:
-        ASCII.Char
-
-    build-depends: ascii-group == 1.0.0.*
-    reexported-modules:
-        ASCII.Group
-
-    build-depends: ascii-case == 1.0.1.*
-    reexported-modules:
         ASCII.Case
-
-    build-depends: ascii-numbers == 1.1.0.*
-    reexported-modules:
-        ASCII.Decimal
+      , ASCII.Caseless
+      , ASCII.CaseRefinement
+      , ASCII.Char
+      , ASCII.Decimal
+      , ASCII.Group
       , ASCII.Hexadecimal
-      , ASCII.Word4
-
-    build-depends: ascii-predicates == 1.0.1.*
-    reexported-modules:
-        ASCII.Predicates
-      , ASCII.Lists
-      , ASCII.ListsAndPredicates
-
-    build-depends: ascii-superset == 1.1.0.*
-    reexported-modules:
-        ASCII.CaseRefinement
       , ASCII.Isomorphism
       , ASCII.Lift
+      , ASCII.Lists
+      , ASCII.ListsAndPredicates
+      , ASCII.Predicates
+      , ASCII.QuasiQuoters
       , ASCII.Refinement
       , ASCII.Superset
-
-    build-depends: ascii-th == 1.1.1.*
-    reexported-modules:
-        ASCII.TemplateHaskell
-      , ASCII.QuasiQuoters
+      , ASCII.TemplateHaskell
+      , ASCII.Word4
 
 test-suite test-ascii
     import: base
     type: exitcode-stdio-1.0
     hs-source-dirs: test
     main-is: Main.hs
-
+    default-extensions: OverloadedStrings QuasiQuotes TemplateHaskell
     build-depends:
         ascii
       , hedgehog ^>= 1.0.5 || ^>= 1.1 || ^>= 1.2
-
-    default-extensions:
-        OverloadedStrings
-        QuasiQuotes
-        TemplateHaskell
diff --git a/changelog.md b/changelog.md
--- a/changelog.md
+++ b/changelog.md
@@ -1,3 +1,14 @@
+### 1.4.0.0
+
+Additions to the `ASCII` module: `disregardCase`, `ASCII'case`, `ASCII'upper`,
+`ASCII'lower`, `KnownCase (..)`, `refineCharToCase`, `refineStringToCase`
+
+Update `ascii-superset` to `1.2.0`. This adds `CharSuperset (toCaseChar)`,
+`StringSuperset (toCaseString)`, `refineCharToCase`, and `refineStringToCase`.
+
+The constraint on `toCaseChar` is relaxed from `CharIso` to `CharSuperset`.
+The constraint on `toCaseString` is relaxed from `StringIso` to `StringSuperset`.
+
 ### 1.3.1.0 (2023-01-03)
 
 Update `ascii-th` to `1.1.1`.
diff --git a/library/ASCII.hs b/library/ASCII.hs
--- a/library/ASCII.hs
+++ b/library/ASCII.hs
@@ -38,6 +38,7 @@
     Group (..), charGroup,  inGroup,
     {- ** Upper/lower case -} {- $case -}
     Case (..), letterCase, isCase, toCaseChar, toCaseString,
+    disregardCase, refineCharToCase, refineStringToCase,
     {- ** Letters  -} isLetter,
     {- ** Letters and numbers  -} isAlphaNum,
     {- ** Decimal digits -} {- $digit -} isDigit, Digit,
@@ -87,7 +88,8 @@
     {- ** @Natural@ ↔ @[HexChar]@ -}
     showNaturalHexChars, readNaturalHexChars,
 
-    {- * Refinement type -} {- $refinement -} ASCII,
+    {- * Refinement types -} {- $refinement -} ASCII,
+    ASCII'case, ASCII'upper, ASCII'lower, KnownCase (..),
 
     {- * Polymorphic conversions -}
     {- ** Narrowing -} toAsciiCharMaybe, toDigitMaybe, toHexCharMaybe,
@@ -115,6 +117,7 @@
   where
 
 import ASCII.Case (Case (..))
+import ASCII.CaseRefinement (KnownCase (..), ASCII'case, ASCII'upper, ASCII'lower, refineCharToCase, refineStringToCase)
 import ASCII.Caseless (CaselessChar)
 import ASCII.Char (Char)
 import ASCII.Decimal (Digit, DigitStringSuperset, DigitSuperset)
@@ -139,6 +142,7 @@
 import Prelude (Integral)
 
 import qualified ASCII.Case
+import qualified ASCII.Caseless
 import qualified ASCII.Decimal
 import qualified ASCII.Group
 import qualified ASCII.Hexadecimal
@@ -251,8 +255,8 @@
 
 -}
 
-toCaseChar :: CharIso char => Case -> char -> char
-toCaseChar c = ASCII.Isomorphism.asChar (ASCII.Case.toCase c)
+toCaseChar :: CharSuperset char => Case -> char -> char
+toCaseChar = ASCII.Superset.toCaseChar
 
 {- | Maps each of the characters in a string to its upper/lower case equivalent.
 
@@ -264,9 +268,14 @@
 
 -}
 
-toCaseString :: StringIso string => Case -> string -> string
-toCaseString c = ASCII.Isomorphism.mapChars (ASCII.Case.toCase c)
+toCaseString :: StringSuperset string => Case -> string -> string
+toCaseString = ASCII.Superset.toCaseString
 
+{-| Convert from ASCII character to caseless ASCII character, discarding the
+case if the character is a letter -}
+disregardCase :: Char -> CaselessChar
+disregardCase = ASCII.Caseless.disregardCase
+
 {- $monomorphicConversions
 
 These are a few simple monomorphic functions to convert between ASCII and types representing some other character set.
@@ -483,7 +492,7 @@
 
 {- $refinement
 
-See also: "ASCII.Refinement"
+See also: "ASCII.Refinement", "ASCII.CaseRefinement"
 
 -}
 
diff --git a/readme.md b/readme.md
--- a/readme.md
+++ b/readme.md
@@ -45,7 +45,7 @@
 
   * The `ascii-numbers` package provides utilities for working with numbers
     represented using ASCII digits 0-9, ASCII letters A-F to represent
-    hexadecimal digits 10-15, and the `HypenMinus` character for negation.
+    hexadecimal digits 10-15, and the `HyphenMinus` character for negation.
 
   * The `ascii-th` package provides a [quasi-quoter][qq] that allows one to
     safely and conveniently express ASCII string literals. The generated