diff --git a/ndn-cpp/publisher-public-key-digest.hpp b/ndn-cpp/publisher-public-key-digest.hpp
index 02009b9..3b8dd56 100644
--- a/ndn-cpp/publisher-public-key-digest.hpp
+++ b/ndn-cpp/publisher-public-key-digest.hpp
@@ -26,7 +26,7 @@
    * WARNING: The resulting pointers in publisherPublicKeyDigestStruct are invalid after a further use of this object which could reallocate memory.
    * @param publisherPublicKeyDigestStruct a C ndn_PublisherPublicKeyDigest struct to receive the pointer
    */
-  void get(struct ndn_PublisherPublicKeyDigest &publisherPublicKeyDigestStruct) const 
+  void get(struct ndn_PublisherPublicKeyDigest& publisherPublicKeyDigestStruct) const 
   {
     publisherPublicKeyDigestStruct.publisherPublicKeyDigestLength = publisherPublicKeyDigest_.size();
     if (publisherPublicKeyDigest_.size() > 0)
@@ -39,16 +39,16 @@
    * Clear this PublisherPublicKeyDigest, and copy from the ndn_PublisherPublicKeyDigest struct.
    * @param excludeStruct a C ndn_Exclude struct
    */
-  void set(const struct ndn_PublisherPublicKeyDigest &publisherPublicKeyDigestStruct) 
+  void set(const struct ndn_PublisherPublicKeyDigest& publisherPublicKeyDigestStruct) 
   {
     setVector(publisherPublicKeyDigest_, publisherPublicKeyDigestStruct.publisherPublicKeyDigest, 
               publisherPublicKeyDigestStruct.publisherPublicKeyDigestLength);
   }
 
-  const std::vector<unsigned char> &getPublisherPublicKeyDigest() const { return publisherPublicKeyDigest_; }
-  std::vector<unsigned char> &getPublisherPublicKeyDigest() { return publisherPublicKeyDigest_; }
+  const std::vector<unsigned char>& getPublisherPublicKeyDigest() const { return publisherPublicKeyDigest_; }
+  std::vector<unsigned char>& getPublisherPublicKeyDigest() { return publisherPublicKeyDigest_; }
 
-  void setPublisherPublicKeyDigest(const std::vector<unsigned char> &publisherPublicKeyDigest) { publisherPublicKeyDigest_ = publisherPublicKeyDigest; }
+  void setPublisherPublicKeyDigest(const std::vector<unsigned char>& publisherPublicKeyDigest) { publisherPublicKeyDigest_ = publisherPublicKeyDigest; }
   void setPublisherPublicKeyDigest(const unsigned char *publisherPublicKeyDigest, unsigned int publisherPublicKeyDigestLength) 
   { 
     setVector(publisherPublicKeyDigest_, publisherPublicKeyDigest, publisherPublicKeyDigestLength);