diff --git a/examples/slm.c b/examples/slm.c
index 5234394..84020a2 100644
--- a/examples/slm.c
+++ b/examples/slm.c
@@ -1,3 +1,4 @@
+#include <assert.h>
 #include <errno.h>
 #include <stddef.h>
 #include <stdint.h>
@@ -125,6 +126,18 @@ main()
   q.key = 0;
   api_skip_remove_slex(list, &q);
 
+  assert(api_skip_gte_slex(list, -3) == -20);
+  assert(api_skip_gte_slex(list, -2) == -20);
+  assert(api_skip_gte_slex(list, 0) == 10);
+  assert(api_skip_gte_slex(list, 2) == 20);
+  assert(api_skip_gte_slex(list, 3) == 0);
+
+  assert(api_skip_lte_slex(list, -3) == 0);
+  assert(api_skip_lte_slex(list, -2) == -20);
+  assert(api_skip_lte_slex(list, 0) == -10);
+  assert(api_skip_lte_slex(list, 2) == 20);
+  assert(api_skip_lte_slex(list, 3) == 20);
+
   FILE *of = fopen("/tmp/slm.dot", "w");
   if (!of) {
     perror("Failed to open file /tmp/slm.dot");
@@ -135,33 +148,6 @@ main()
 
   api_skip_destroy_slex(list);
 
-#if 0
-  /* Delete a specific element in the list. */
-  struct slex_node query;
-  query.key = 4;
-  struct slex_node *removed = SKIP_REMOVE(list, q, entries);
-  free(removed);
-  /* Forward traversal. */
-  SKIP_FOREACH(np, &head, entries)
-    np-> ...
-    /* Reverse traversal. */
-    SKIP_FOREACH_REVERSE(np, &head, skiphead, entries)
-    np-> ...
-    /* Skiplist Deletion. */
-    while (!SKIP_EMPTY(&head)) {
-      n1 = SKIP_FIRST(&head);
-      SKIP_REMOVE(&head, n1, entries);
-      free(n1);
-    }
-  /* Faster Skiplist Deletion. */
-  n1 = SKIP_FIRST(&head);
-  while (n1 != NULL) {
-    n2 = SKIP_NEXT(n1, entries);
-    free(n1);
-    n1 = n2;
-  }
-  SKIP_INIT(&head);
-#endif
 fail:;
   return rc;
 }
diff --git a/include/sl.h b/include/sl.h
index 0ad91ac..e408cea 100644
--- a/include/sl.h
+++ b/include/sl.h
@@ -249,7 +249,7 @@
     decl##_node_t **path;                                                    \
     decl##_node_t *elm = slist->slh_head;                                    \
                                                                              \
-    if (!slist || !n)                                                        \
+    if (slist == NULL || n == NULL)                                          \
       return NULL;                                                           \
                                                                              \
     i = slist->max + 1;                                                      \
@@ -349,10 +349,9 @@
     unsigned int i;                                                          \
     decl##_node_t *elm = slist->slh_head;                                    \
                                                                              \
-    if (!slist || !n)                                                        \
+    if (slist == NULL || n == NULL)                                          \
       return NULL;                                                           \
                                                                              \
-    i = slist->max + 1;                                                      \
     i = slist->level;                                                        \
                                                                              \
     do {                                                                     \
@@ -374,13 +373,13 @@
   decl##_node_t *prefix##skip_find_gte_##decl(decl##_t *slist,               \
     decl##_node_t *n)                                                        \
   {                                                                          \
+    int cmp;                                                                 \
     unsigned int i;                                                          \
     decl##_node_t *elm = slist->slh_head;                                    \
                                                                              \
-    if (!slist || !n)                                                        \
+    if (slist == NULL || n == NULL)                                          \
       return NULL;                                                           \
                                                                              \
-    i = slist->max + 1;                                                      \
     i = slist->level;                                                        \
                                                                              \
     do {                                                                     \
@@ -389,7 +388,10 @@
           slist->aux) < 0)                                                   \
         elm = elm->field.sle_next[i];                                        \
     } while (i--);                                                           \
-    elm = elm->field.sle_next[0];                                            \
+    do {                                                                     \
+      elm = elm->field.sle_next[0];                                          \
+      cmp = __skip_key_compare_##decl(slist, elm, n, slist->aux);            \
+    } while (cmp < 0);                                                       \
     return elm;                                                              \
   }                                                                          \
                                                                              \
@@ -399,13 +401,13 @@
   decl##_node_t *prefix##skip_find_lte_##decl(decl##_t *slist,               \
     decl##_node_t *n)                                                        \
   {                                                                          \
+    int cmp;                                                                 \
     unsigned int i;                                                          \
     decl##_node_t *elm = slist->slh_head;                                    \
                                                                              \
-    if (!slist || !n)                                                        \
+    if (slist == NULL || n == NULL)                                          \
       return NULL;                                                           \
                                                                              \
-    i = slist->max + 1;                                                      \
     i = slist->level;                                                        \
                                                                              \
     do {                                                                     \
@@ -414,9 +416,14 @@
           slist->aux) < 0)                                                   \
         elm = elm->field.sle_next[i];                                        \
     } while (i--);                                                           \
-    if (__skip_key_compare_##decl(slist, elm->field.sle_next[0], n,          \
-          slist->aux) == 0) {                                                \
-      return elm->field.sle_next[0];                                         \
+    elm = elm->field.sle_next[0];                                            \
+    if (__skip_key_compare_##decl(slist, elm, n, slist->aux) == 0) {         \
+      return elm;                                                            \
+    } else {                                                                 \
+      do {                                                                   \
+        elm = elm->field.sle_prev;                                           \
+        cmp = __skip_key_compare_##decl(slist, elm, n, slist->aux);          \
+      } while (cmp > 0);                                                     \
     }                                                                        \
     return elm;                                                              \
   }                                                                          \
@@ -431,7 +438,7 @@
   {                                                                          \
     decl##_node_t *node;                                                     \
                                                                              \
-    if (!slist || !new)                                                      \
+    if (slist == NULL || new == NULL)                                        \
       return -1;                                                             \
                                                                              \
     node = prefix##skip_find_##decl(slist, new);                             \
@@ -448,7 +455,7 @@
     size_t i, s;                                                             \
     decl##_node_t **path, *node;                                             \
                                                                              \
-    if (!slist || !n)                                                        \
+    if (slist == NULL || n == NULL)                                          \
       return -1;                                                             \
     if (slist->length == 0)                                                  \
       return 0;                                                              \
@@ -484,7 +491,7 @@
   decl##_node_t *prefix##skip_next_node_##decl(decl##_t *slist,              \
     decl##_node_t *n)                                                        \
   {                                                                          \
-    if (!slist || !n)                                                        \
+    if (slist == NULL || n == NULL)                                          \
       return NULL;                                                           \
     if (n->field.sle_next[0] == slist->slh_tail)                             \
       return NULL;                                                           \
@@ -495,7 +502,7 @@
   decl##_node_t *prefix##skip_prev_node_##decl(decl##_t *slist,              \
     decl##_node_t *n)                                                        \
   {                                                                          \
-    if (!slist || !n)                                                        \
+    if (slist == NULL || n == NULL)                                          \
       return NULL;                                                           \
     if (n->field.sle_prev == slist->slh_head)                                \
       return NULL;                                                           \
@@ -506,7 +513,7 @@
   int prefix##skip_destroy_##decl(decl##_t *slist)                           \
   {                                                                          \
     decl##_node_t *node, *next;                                              \
-    if (!slist)                                                              \
+    if (slist == NULL)                                                       \
       return 0;                                                              \
     if (prefix##skip_size_##decl(slist) == 0)                                \
       return 0;                                                              \