diff --git a/algs4/frequency_counter.py b/algs4/frequency_counter.py
index 202a191..3be38a0 100644
--- a/algs4/frequency_counter.py
+++ b/algs4/frequency_counter.py
@@ -23,10 +23,14 @@
 """
 
 import sys
-from algs4.sequential_search_st import SequentialSearchST
+# from algs4.sequential_search_st import SequentialSearchST
+#from algs4.binary_search_st import BinarySearchST
+from algs4.red_black_bst import RedBlackBST
 
 minlen = int(sys.argv[1])
-st = SequentialSearchST()
+# st = SequentialSearchST()
+#st = BinarySearchST()
+st = RedBlackBST()
 
 for line in sys.stdin:
     words = line.split()
@@ -40,7 +44,7 @@
 
 maxstr = ""
 st.put(maxstr, 0)
-for word in st.keys():
+for word in st.Keys():
     if st.get(word) > st.get(maxstr):
         maxstr = word
 print(maxstr, " ", st.get(maxstr))
diff --git a/algs4/red_black_bst.py b/algs4/red_black_bst.py
index f99250a..186d391 100644
--- a/algs4/red_black_bst.py
+++ b/algs4/red_black_bst.py
@@ -174,7 +174,7 @@ def level_order(self):
             queue.enqueue(x.right)
         return keys
 
-    def keys(self):
+    def Keys(self):
         """
          Returns all keys in the symbol table
          To iterate over all of the keys in the symbol table named {@code st},
@@ -309,7 +309,7 @@ def _delete(self, h, key):
                 h = self.move_red_right(h)
 
             if key == h.key:
-                x = self.min(h.right)
+                x = self._min(h.right)
                 h.key = x.key
                 h.val = x.val
                 h.right = self._delete_min(h.right)
@@ -325,9 +325,9 @@ def delete_min(self):
         if not self.is_red(self.root.left) and not self.is_red(self.root.right):
             self.root.color = RedBlackBST.RED
 
-        self.root = self._deleteMin(self.root)
-        if not is_empty(self.root):
-            self.root.color = RedBlackBST.BLACk
+        self.root = self._delete_min(self.root)
+        if not self.is_empty():
+            self.root.color = RedBlackBST.BLACK
 
     def _delete_min(self, h):
         if h.left is None:
@@ -335,7 +335,7 @@ def _delete_min(self, h):
         if not self.is_red(h.left) and not self.is_red(h.left.left):
             h = self.move_red_left(h)
 
-        h.left = self._deleteMin(h.left)
+        h.left = self._delete_min(h.left)
         return self.balance(h)
 
     def balance(self, h):
@@ -348,6 +348,7 @@ def balance(self, h):
         h.size = self._size(h.left) + self._size(h.right) + 1
         return h
 
+
 if __name__ == '__main__':
     import sys
 
diff --git a/algs4/sequential_search_st.py b/algs4/sequential_search_st.py
index 1e89486..816836f 100644
--- a/algs4/sequential_search_st.py
+++ b/algs4/sequential_search_st.py
@@ -71,7 +71,7 @@ def delete(self, key):
             prev = curr
             curr = curr.next
 
-    def keys(self):
+    def Keys(self):
         return STKeyIterator(self.first)
 
     def is_empty(self):