diff --git a/lib/tdm_datatype.hpp b/lib/tdm_datatype.hpp
index bc0a3c4..e59db3d 100644
--- a/lib/tdm_datatype.hpp
+++ b/lib/tdm_datatype.hpp
@@ -17,6 +17,7 @@ typedef double eFloat64Usi;
 
 class tdmdatatype
 {
+
 protected:
   eInt16Usi sint16_;    // 0
   eInt32Usi sint32_;    // 1
@@ -26,6 +27,7 @@ protected:
   eFloat32Usi float32_; // 5
   eFloat64Usi float64_; // 6
   short int dtidx_;     // \in \{0,...,6\}
+
 public:
   tdmdatatype(): sint16_(0), sint32_(0),
                  uint8_(0), uint16_(0), uint32_(0),
@@ -43,6 +45,19 @@ public:
   // identify type
   short int& dtype() { return dtidx_; }
 
+  // copy constructor
+  tdmdatatype(const tdmdatatype &num)
+  {
+    this->sint16_ = num.sint16_;
+    this->sint32_ = num.sint32_;
+    this->uint8_ = num.uint8_;
+    this->uint16_ = num.uint16_;
+    this->uint32_ = num.uint32_;
+    this->float32_ = num.float32_;
+    this->float64_ = num.float64_;
+    this->dtidx_ = num.dtidx_;
+  }
+
   // overall assignment operator
   tdmdatatype& operator=(const tdmdatatype &num)
   {
@@ -55,9 +70,10 @@ public:
       this->uint32_ = num.uint32_;
       this->float32_ = num.float32_;
       this->float64_ = num.float64_;
+      this->dtidx_ = num.dtidx_;
     }
 
-		return *this;
+    return *this;
   }
 
   // implement assignment operator for individual datatypes
diff --git a/lib/tdm_termite.cpp b/lib/tdm_termite.cpp
index 7482a5e..82266ae 100644
--- a/lib/tdm_termite.cpp
+++ b/lib/tdm_termite.cpp
@@ -568,7 +568,7 @@ template std::string tdm_termite::get_overview<submatrix>(format formatter);
 template std::string tdm_termite::get_overview<localcolumn>(format formatter);
 template std::string tdm_termite::get_overview<block>(format formatter);
 
-void tdm_termite::summarize_member(tdm_channelgroup chp, std::string& summary, format& formatter)
+void tdm_termite::summarize_member(tdm_channelgroup &chp, std::string& summary, format& formatter)
 {
   for ( std::map<std::string,tdm_channelgroup>::iterator it=this->tdmchannelgroups_.begin();
                                                          it!=this->tdmchannelgroups_.end(); ++it)
@@ -578,7 +578,7 @@ void tdm_termite::summarize_member(tdm_channelgroup chp, std::string& summary, f
   }
 }
 
-void tdm_termite::summarize_member(submatrix sbm, std::string& summary, format& formatter)
+void tdm_termite::summarize_member(submatrix &sbm, std::string& summary, format& formatter)
 {
   for ( std::map<std::string,submatrix>::iterator it=this->submatrices_.begin();
                                                   it!=this->submatrices_.end(); ++it)
@@ -588,7 +588,7 @@ void tdm_termite::summarize_member(submatrix sbm, std::string& summary, format&
   }
 }
 
-void tdm_termite::summarize_member(localcolumn lcc, std::string& summary, format& formatter)
+void tdm_termite::summarize_member(localcolumn &lcc, std::string& summary, format& formatter)
 {
   for ( std::map<std::string,localcolumn>::iterator it=this->localcolumns_.begin();
                                                     it!=this->localcolumns_.end(); ++it)
@@ -598,7 +598,7 @@ void tdm_termite::summarize_member(localcolumn lcc, std::string& summary, format
   }
 }
 
-void tdm_termite::summarize_member(block blk, std::string& summary, format& formatter)
+void tdm_termite::summarize_member(block &blk, std::string& summary, format& formatter)
 {
   for ( std::map<std::string,block>::iterator it=this->tdx_blocks_.begin();
                                               it!=this->tdx_blocks_.end(); ++it)
diff --git a/lib/tdm_termite.hpp b/lib/tdm_termite.hpp
index 454ae1c..2b09e36 100644
--- a/lib/tdm_termite.hpp
+++ b/lib/tdm_termite.hpp
@@ -184,10 +184,10 @@ public:
   template<typename tdmelement>
   std::string get_overview(format formatter);
 private:
-  void summarize_member(tdm_channelgroup chp, std::string& summary, format& formatter);
-  void summarize_member(submatrix sbm, std::string& summary, format& formatter);
-  void summarize_member(localcolumn lcc, std::string& summary, format& formatter);
-  void summarize_member(block blk, std::string& summary, format& formatter);
+  void summarize_member(tdm_channelgroup &chp, std::string& summary, format& formatter);
+  void summarize_member(submatrix &sbm, std::string& summary, format& formatter);
+  void summarize_member(localcolumn &lcc, std::string& summary, format& formatter);
+  void summarize_member(block &blk, std::string& summary, format& formatter);
 public:
 
   // get list of channelgroup ids
diff --git a/pip/setup.py b/pip/setup.py
index 21be9af..d121c12 100644
--- a/pip/setup.py
+++ b/pip/setup.py
@@ -1,6 +1,5 @@
 
 from setuptools import setup, Extension
-import os
 
 with open("README.md", "r", encoding="utf-8") as fh:
     long_description = fh.read()