diff --git a/lawful-conversions.cabal b/lawful-conversions.cabal
--- a/lawful-conversions.cabal
+++ b/lawful-conversions.cabal
@@ -1,6 +1,6 @@
 cabal-version: 3.0
 name: lawful-conversions
-version: 0.3.0.3
+version: 0.3.0.4
 synopsis: Lawful typeclasses for bidirectional conversion between types
 category: Conversion
 homepage: https://github.com/nikita-volkov/lawful-conversions
@@ -92,6 +92,7 @@
     LawfulConversions.Proxies
     LawfulConversions.Proxies.ViaIsSome
     LawfulConversions.Relations
+    LawfulConversions.Relations.Any
     LawfulConversions.Relations.BoxedVectorAndList
     LawfulConversions.Relations.BoxedVectorAndSeq
     LawfulConversions.Relations.ByteArrayAndByteString
@@ -154,6 +155,7 @@
     LawfulConversions.Relations.TextAndUtcTime
     LawfulConversions.Relations.TextAndUuid
     LawfulConversions.Relations.TextArrayAndWord8List
+    LawfulConversions.Relations.Void
     LawfulConversions.TextCompat.Array
 
   build-depends:
diff --git a/src/library/LawfulConversions/Algebra.hs b/src/library/LawfulConversions/Algebra.hs
--- a/src/library/LawfulConversions/Algebra.hs
+++ b/src/library/LawfulConversions/Algebra.hs
@@ -52,18 +52,8 @@
   default maybeFrom :: (IsSome b a) => a -> Maybe b
   maybeFrom = Just . to
 
--- | Every type is isomorphic to itself.
-instance IsSome a a where
-  to = id
-  maybeFrom = Just . id
-
--- | The empty set has no elements, and therefore is vacuously a subset of any set.
-instance IsSome a Void where
-  to = absurd
-  maybeFrom = const Nothing
-
 -- |
--- Convert a value of a superset type to a subset type specifying the superset type first.
+-- Convert a value of a subset type to a superset type, specifying the source subset type first.
 --
 -- Alias to 'to' with the only difference in the argument order.
 --
@@ -108,7 +98,7 @@
 --
 -- Every value of type @b@ can be obtained by applying 'onfrom' to some value of type @a@:
 --
--- > \b -> exists a. onfrom @b a == b
+-- > \b -> exists a. onfrom @a @b a == b
 --
 -- Note: This property cannot be directly tested with QuickCheck as it requires existential quantification.
 --
@@ -158,8 +148,6 @@
 onto :: forall b a. (IsMany a b) => a -> b
 onto = onfrom
 
-instance IsMany a a
-
 -- | Bidirectional conversion between two types with no loss of information.
 --
 -- The bidirectionality is encoded via a recursive dependency with arguments
@@ -173,13 +161,13 @@
 --
 -- For all values of /b/ converting from /b/ to /a/ and then converting from /a/ to /b/ produces the original value:
 --
--- > \b -> b == from @b (to @a b)
+-- > \b -> b == from @a (to @a b)
 --
 -- ==== 'to' is an [inverse](https://en.wikipedia.org/wiki/Inverse_function) of 'from'
 --
 -- For all values of /a/ converting from /a/ to /b/ and then converting from /b/ to /a/ produces the original value:
 --
--- > \a -> a == to @a (from @b a)
+-- > \a -> a == to @a (from @a @b a)
 --
 -- ==== Mathematical relationship
 --
@@ -190,7 +178,7 @@
 --
 -- For isomorphic types, both ways of converting should be equivalent:
 --
--- > \a -> from @b @a a == onfrom @a @b a
+-- > \a -> from @a @b a == onfrom @a @b a
 --
 -- === Testing
 --
@@ -220,6 +208,3 @@
 -- instance Is "Data.Text.Text" "Data.Text.Lazy.LazyText"
 -- @
 class (IsMany a b, Is b a) => Is a b
-
--- | Any type is isomorphic to itself.
-instance Is a a
diff --git a/src/library/LawfulConversions/Relations.hs b/src/library/LawfulConversions/Relations.hs
--- a/src/library/LawfulConversions/Relations.hs
+++ b/src/library/LawfulConversions/Relations.hs
@@ -1,5 +1,6 @@
 module LawfulConversions.Relations () where
 
+import LawfulConversions.Relations.Any ()
 import LawfulConversions.Relations.BoxedVectorAndList ()
 import LawfulConversions.Relations.BoxedVectorAndSeq ()
 import LawfulConversions.Relations.ByteArrayAndByteString ()
@@ -62,3 +63,4 @@
 import LawfulConversions.Relations.TextAndUtcTime ()
 import LawfulConversions.Relations.TextAndUuid ()
 import LawfulConversions.Relations.TextArrayAndWord8List ()
+import LawfulConversions.Relations.Void ()
diff --git a/src/library/LawfulConversions/Relations/Any.hs b/src/library/LawfulConversions/Relations/Any.hs
new file mode 100644
--- /dev/null
+++ b/src/library/LawfulConversions/Relations/Any.hs
@@ -0,0 +1,17 @@
+{-# OPTIONS_GHC -Wno-orphans #-}
+
+module LawfulConversions.Relations.Any where
+
+import LawfulConversions.Algebra
+import LawfulConversions.Prelude
+
+-- | Any type is isomorphic to itself.
+instance IsSome a a where
+  to = id
+  maybeFrom = Just . id
+
+-- | Any type is isomorphic to itself.
+instance IsMany a a
+
+-- | Any type is isomorphic to itself.
+instance Is a a
diff --git a/src/library/LawfulConversions/Relations/Void.hs b/src/library/LawfulConversions/Relations/Void.hs
new file mode 100644
--- /dev/null
+++ b/src/library/LawfulConversions/Relations/Void.hs
@@ -0,0 +1,11 @@
+{-# OPTIONS_GHC -Wno-orphans #-}
+
+module LawfulConversions.Relations.Void where
+
+import LawfulConversions.Algebra
+import LawfulConversions.Prelude
+
+-- | The empty set has no elements, and therefore is vacuously a subset of any set.
+instance IsSome a Void where
+  to = absurd
+  maybeFrom = const Nothing