diff --git a/src/flow/binary.rs b/src/flow/binary.rs
index 8f3bc7f..41fe14b 100644
--- a/src/flow/binary.rs
+++ b/src/flow/binary.rs
@@ -133,7 +133,6 @@ pub trait BinaryTreesMutable<'a>: BinaryTreesEmpty<'a> + BinaryTreesTreeOf<'a> {
 
 pub trait BinaryTreesHeight<'a>: BinaryTrees<'a> {
     fn height(&self, tree: &Self::Tree) -> u64;
-    fn height_r(&self, reference: &Self::Reference) -> u64;
     fn leaf_height_error<T: 'a>(&self, height: u64) -> BTWrap<'a, Self, T>;
 }
 
diff --git a/src/flow/binary/bounds/bound.rs b/src/flow/binary/bounds/bound.rs
index 89cad47..8848fe2 100644
--- a/src/flow/binary/bounds/bound.rs
+++ b/src/flow/binary/bounds/bound.rs
@@ -155,10 +155,6 @@ impl<'a, BT: BinaryTreesBindable<'a> + BinaryTreesHeight<'a>> BinaryTreesHeight<
         self.0.height(&tree.bound)
     }
 
-    fn height_r(&self, reference: &Self::Reference) -> u64 {
-        self.0.height_r(&reference.bound)
-    }
-
     fn leaf_height_error<T: 'a>(&self, height: u64) -> BTWrap<'a, Self, T> {
         self.0.leaf_height_error(height)
     }
diff --git a/src/mrds/trees/avl.rs b/src/mrds/trees/avl.rs
index 9a1eca9..f1d017a 100644
--- a/src/mrds/trees/avl.rs
+++ b/src/mrds/trees/avl.rs
@@ -181,10 +181,6 @@ impl<'a, A: 'a + PartialOrd + Clone> BinaryTreesHeight<'a> for AvlTs<A> {
         tree.height
     }
 
-    fn height_r(&self, reference: &Self::Reference) -> u64 {
-        reference.height
-    }
-
     fn leaf_height_error<T: 'a>(&self, height: u64) -> BTWrap<'a, Self, T> {
         panic!("leaf height error: {height}.")
     }
diff --git a/src/rstd/collections/avl/context.rs b/src/rstd/collections/avl/context.rs
index 3d25987..eb2afb9 100644
--- a/src/rstd/collections/avl/context.rs
+++ b/src/rstd/collections/avl/context.rs
@@ -108,10 +108,6 @@ impl<'a, Ctx: Context<'a>, A: Mentionable<'a, Ctx> + Clone, C: 'a + Comparator<A
         tree.height()
     }
 
-    fn height_r(&self, reference: &Self::Reference) -> u64 {
-        reference.height()
-    }
-
     fn leaf_height_error<T: 'a>(&self, height: u64) -> BTWrap<'a, Self, T> {
         <FallibleMonad<'a, Ctx, _> as Fail<_>>::fail(ResolutionError::Parse(BoundError::Avl(
             AvlError::LeafHeight(height),