diff --git a/dnstool.py b/dnstool.py
index 8c2183b..e0cea8c 100644
--- a/dnstool.py
+++ b/dnstool.py
@@ -121,9 +121,11 @@ class DnsCase:
         Read Single DNS Data File
         '''
 
-        offset_data = (4+8*6+4) + (4+8*3+4) + 3 * (4+8*2+4) + 4
+        import numpy as np
 
-        info = read_info(fname)
+        offset_data = self.data_start
+
+        info_dict = self.read_info(fname)
 
         t  = info_dict['time']
         nx = info_dict['nx']
@@ -146,9 +148,11 @@ class DnsCase:
         Read Single DNS Data File
         '''
 
+        import numpy as np
+
         offset_data = self.data_start
 
-        info = read_info(fname)
+        info_dict = self.read_info(fname)
 
         t  = info_dict['time']
         nx = info_dict['nx']
@@ -166,6 +170,11 @@ class DnsCase:
 
 
 def case_library ():
+    '''
+    Return DNS case object library
+    '''
+
+    import os
 
     cases = '''
     IC1 /home1/dhkim/4pi_IC1/4pi_IC1_01_kfmax10_lt58