diff --git a/ax_init_standard_project.m4 b/ax_init_standard_project.m4
index 26735b3..9fdc7dd 100644
--- a/ax_init_standard_project.m4
+++ b/ax_init_standard_project.m4
@@ -298,15 +298,79 @@ EOF
 
 AC_DEFUN([AX_PKG_REQUIRE], [
   PKG_PROG_PKG_CONFIG
-  PKG_CHECK_MODULES([$1], [$1], [
+  PKG_CHECK_MODULES([$1], [$2], [
+    if test -n "$3"; then
+      $1_found=0;
+      for p in ${$1_CFLAGS}; do
+        if test -e ${p#-I}/$3; then
+          $1_found=1
+          break
+        fi
+      done
+      if test ${$1_found} -eq 0; then
+        for p in /usr/include ${$1_CFLAGS}; do
+          $1_file=$(find ${p#-I} -name $3)
+          if test -e ${$1_file}; then
+            $1_CFLAGS="${$1_CFLAGS} -I${$1_file%/*}"
+            $1_found=1
+            break
+          fi
+        done
+      fi
+      if test ${$1_found} -eq 0; then
+        AC_MSG_WARN([Header file $3 not found in $1_CFLAGS = ${$1_CFLAGS}])
+      fi
+    fi
     AM_CPPFLAGS+=" ${$1_CFLAGS}"
     AM_CXXFLAGS+=" ${$1_CFLAGS}"
     LIBS+=" ${$1_LIBS}"
   ], [
-    AC_MSG_ERROR([Required package $1 not found])
+    AC_MSG_WARN([Recommended package $2 for feature $1 not installed])
+    if test -n "$4"; then
+      for pkg in $4; do
+        PKG_CHECK_MODULES([$1], [$pkg], [
+          if test -n "$3"; then
+            $1_found=0;
+            for p in ${$1_CFLAGS}; do
+              if test -e ${p#-I}/$3; then
+                $1_found=1
+                break
+              fi
+            done
+            if test ${$1_found} -eq 0; then
+              for p in /usr/include ${$1_CFLAGS}; do
+                $1_file=$(find ${p#-I} -name $3)
+                if test -e ${$1_file}; then
+                  $1_CFLAGS="${$1_CFLAGS} -I${$1_file%/*}"
+                  $1_found=1
+                  break
+                fi
+              done
+            fi
+            if test ${$1_found} -eq 0; then
+              AC_MSG_WARN([Header file $3 not found in $1_CFLAGS = ${$1_CFLAGS}])
+            fi
+          fi
+          AM_CPPFLAGS+=" ${$1_CFLAGS}"
+          AM_CXXFLAGS+=" ${$1_CFLAGS}"
+          LIBS+=" ${$1_LIBS}"
+        ], [
+          AC_MSG_WARN([Recommended package $pkg for feature $1 not installed])
+        ])
+      done
+    fi
   ])
   AC_SUBST(AM_CPPFLAGS)
   AC_SUBST(AM_CXXFLAGS)
+  if test -n "$3"; then
+    old_CPPFLAGS=${CPPFLAGS}
+    CPPFLAGS=" ${$1_CFLAGS} ${CPPFLAGS}"
+    AC_CHECK_HEADER([$3], [
+    ], [
+      AC_MSG_ERROR([Required header $3 for feature $1 not found])
+    ])
+    CPPFLAGS=${old_CPPFLAGS}
+  fi
 ])
 
 AC_DEFUN([AX_PKG_CHECK], [
diff --git a/configure.ac b/configure.ac
index dd41277..8994caf 100644
--- a/configure.ac
+++ b/configure.ac
@@ -17,17 +17,7 @@ AX_USE_RPM_PACKAGING
 #AX_USE_CPPUNIT
 AX_BUILD_EXAMPLES
 
-# qt features
-AX_CHECK_QT([QTGUI], [QtCore QtGui], [QtWidgets])
-AX_CHECK_QT([QTNETWORK], [QtNetwork])
-CPPFLAGS="${CPPFLAGS} -DQT_NO_KEYWORDS"
-
-# libraries used
-AX_PKG_REQUIRE([libpcsclite])
-AX_PKG_REQUIRE([libssl])
-#AX_PKG_REQUIRE([libmrw-c++])
-
-# libraries
+# special optional library download
 AC_ARG_ENABLE(pkcs11-download,
   [AS_HELP_STRING([--enable-pkcs11-download],
                   [download pkcs11 header])],
@@ -42,10 +32,17 @@ AC_ARG_ENABLE(pkcs11-download,
      cd -
    fi
   ])
-dnl problem in libs: -Wshadow -Wcast-qual
-dnl auto.hpp: -Wno-ctor-dtor-privacy (removed)
-AC_CHECK_HEADER([pkcs11.h], [], [AC_MSG_ERROR([Header pkcs11.h is required])])
-AC_CHECK_HEADER([mrw/checkcxx11.hxx], [], [AC_MSG_ERROR([please install mrw-c++])])
+
+# qt features
+AX_CHECK_QT([QTGUI], [QtCore QtGui], [QtWidgets])
+AX_CHECK_QT([QTNETWORK], [QtNetwork])
+CPPFLAGS="${CPPFLAGS} -DQT_NO_KEYWORDS"
+
+# libraries used
+AX_PKG_REQUIRE([pcsc], [libpcsclite], [pcsclite.h])
+AX_PKG_REQUIRE([ssl], [libssl], [openssl/crypto.h])
+AX_PKG_REQUIRE([mrwcxx], [mrw-c++])
+AX_PKG_REQUIRE([pkcs11], [p11-kit-1], [pkcs11.h], [gnutls libpkcs11-helper-1])
 
 # create output
 AC_OUTPUT