code style: Don't use std:: inside .cpp files.
diff --git a/ndn-cpp/encoding/der/der.cpp b/ndn-cpp/encoding/der/der.cpp
index 6d269c1..fc31161 100644
--- a/ndn-cpp/encoding/der/der.cpp
+++ b/ndn-cpp/encoding/der/der.cpp
@@ -297,7 +297,7 @@
   DerNode::encodeHeader(payload_.size());
 }
 
-DerByteString::DerByteString(const std::vector<uint8_t>& blob, DerType type)
+DerByteString::DerByteString(const vector<uint8_t>& blob, DerType type)
   :DerNode(type)
 {
   payload_.insert(payload_.end(), blob.begin(), blob.end());
diff --git a/ndn-cpp/encoding/der/visitor/print-visitor.cpp b/ndn-cpp/encoding/der/visitor/print-visitor.cpp
index ab56b5d..cba5d2d 100644
--- a/ndn-cpp/encoding/der/visitor/print-visitor.cpp
+++ b/ndn-cpp/encoding/der/visitor/print-visitor.cpp
@@ -50,7 +50,7 @@
   const string& indent = ndnboost::any_cast<const string&>(param);
       
   printData(derBStr.getHeader(), indent);
-  const std::vector<uint8_t>& payload = derBStr.getPayload();
+  const vector<uint8_t>& payload = derBStr.getPayload();
   cout << indent << "   " << " " << hex << setw(2) << setfill('0') << (int)(uint8_t)payload[0] << endl;
   printData(payload, indent + "   ", 1);
 }