diff --git a/examples/src/butter_ap_zp_test.c b/examples/src/butter_ap_zp_test.c
index 4581024..b2a7056 100644
--- a/examples/src/butter_ap_zp_test.c
+++ b/examples/src/butter_ap_zp_test.c
@@ -28,7 +28,7 @@ int main(int argc, char* argv[])
   /* print H(s) zeros values */
   printf("Butterworth filter zeros: %d\n", nz);
   for(k = 0; k < nz; k++)
-    printf("z[%2d] = %9.3f %+9.3f j\n", k, RE(z[k]), IM(p[k]));
+    printf("z[%2d] = %9.3f %+9.3f j\n", k, RE(z[k]), IM(z[k]));
   
   /* print H(s) poles values */
   printf("Butterworth filter poles: %d\n", np);
diff --git a/examples/src/cheby1_ap_zp_test.c b/examples/src/cheby1_ap_zp_test.c
new file mode 100644
index 0000000..799f8ad
--- /dev/null
+++ b/examples/src/cheby1_ap_zp_test.c
@@ -0,0 +1,59 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "dspl.h"
+
+/* Filter order */
+#define ORD    7
+
+int main(int argc, char* argv[])
+{
+  void* hdspl;  /* DSPL handle        */
+  void* hplot;  /* GNUPLOT handle     */
+  
+  /* Load DSPL functions */
+  hdspl = dspl_load();
+
+  complex_t z[ORD+1]; /* H(s) zeros vector */
+  complex_t p[ORD+1]; /* H(s) poles vector */
+  double Rp = 0.5;    /* Magnitude ripple from 0 to 1 rad/s */
+
+  int res, k, nz, np;
+
+  /* Zeros and poles vectors calculation */
+  res = cheby1_ap_zp(ORD, Rp, z, &nz, p, &np);
+  if(res != RES_OK)
+    printf("error code = 0x%8x\n", res);
+
+  /* print H(s) zeros values */
+  printf("Chebyshev type 1 filter zeros: %d\n", nz);
+  for(k = 0; k < nz; k++)
+    printf("z[%2d] = %9.3f %+9.3f j\n", k, RE(z[k]), IM(z[k]));
+  
+  /* print H(s) poles values */
+  printf("Chebyshev type 1 filter poles: %d\n", np);
+  for(k = 0; k < np; k++)
+    printf("p[%2d] = %9.3f %+9.3f j\n", k, RE(p[k]), IM(p[k]));
+
+  /* Write complex poles to the file */
+  writetxt_cmplx(p, ORD, "dat/cheby1_ap_zp.txt");
+
+  /* plotting by GNUPLOT */
+  gnuplot_create(argc, argv, 440, 360, "img/cheby1_ap_zp_test.png", &hplot);
+  gnuplot_cmd(hplot, "unset key");
+  gnuplot_cmd(hplot, "set xzeroaxis");
+  gnuplot_cmd(hplot, "set yzeroaxis");
+  gnuplot_cmd(hplot, "set xlabel 'sigma'");
+  gnuplot_cmd(hplot, "set ylabel 'jw'");
+  gnuplot_cmd(hplot, "set size square");
+  gnuplot_cmd(hplot, "set xrange [-1.5:1.5]");
+  gnuplot_cmd(hplot, "set yrange [-1.5:1.5]");
+  gnuplot_cmd(hplot, "plot 'dat/cheby1_ap_zp.txt'  with points pt 2");
+  gnuplot_close(hplot); 
+
+  /* free dspl handle */
+  dspl_free(hdspl);
+
+  return res;
+}
+
diff --git a/examples/src/cheby2_ap_zp_test.c b/examples/src/cheby2_ap_zp_test.c
index 2fc9469..a703909 100644
--- a/examples/src/cheby2_ap_zp_test.c
+++ b/examples/src/cheby2_ap_zp_test.c
@@ -1,32 +1,60 @@
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 #include "dspl.h"
 
-#define ORD 7
+/* Filter order */
+#define ORD    7
 
-int main()
+int main(int argc, char* argv[])
 {
-    void* handle;           /* DSPL handle        */
-    handle = dspl_load();   /* Load DSPL functions */
+  void* hdspl;  /* DSPL handle        */
+  void* hplot;  /* GNUPLOT handle     */
+  
+  /* Load DSPL functions */
+  hdspl = dspl_load();
 
-    complex_t z[ORD], p[ORD];    
-    int nz, np, k;
-    double Rs = 40.0;
-    
-    int res = cheby2_ap_zp(ORD, Rs, z, &nz, p, &np);
-    if(res != RES_OK)
-        printf("error code = 0x%8x\n", res);
-    
-    printf("\nChebyshev type 2 zeros:\n");
-    for(k = 0; k < nz; k++)
-        printf("z[%2d] = %9.3f  %9.3f j\n", k, RE(z[k]), IM(z[k]));
+  complex_t z[ORD+1]; /* H(s) zeros vector */
+  complex_t p[ORD+1]; /* H(s) poles vector */
+  double Rs = 40;     /* Stopband suppression, dB */
 
-    printf("\nChebyshev type 2 poles:\n");
-    for(k = 0; k < np; k++)
-        printf("p[%2d] = %9.3f  %9.3f j\n", k, RE(p[k]), IM(p[k]));
+  int res, k, nz, np;
 
-    dspl_free(handle);      /* free dspl handle */
-    return 0;
+  /* Zeros and poles vectors calculation */
+  res = cheby2_ap_zp(ORD, Rs, z, &nz, p, &np);
+  if(res != RES_OK)
+    printf("error code = 0x%8x\n", res);
+
+  /* print H(s) zeros values */
+  printf("Chebyshev type 2 filter zeros: %d\n", nz);
+  for(k = 0; k < nz; k++)
+    printf("z[%2d] = %9.3f %+9.3f j\n", k, RE(z[k]), IM(z[k]));
+  
+  /* print H(s) poles values */
+  printf("Chebyshev type 2 filter poles: %d\n", np);
+  for(k = 0; k < np; k++)
+    printf("p[%2d] = %9.3f %+9.3f j\n", k, RE(p[k]), IM(p[k]));
+
+  /* Write complex poles to the file */
+  writetxt_cmplx(z, nz, "dat/cheby2_ap_z.txt");
+  writetxt_cmplx(p, np, "dat/cheby2_ap_p.txt");
+  /* plotting by GNUPLOT */
+  gnuplot_create(argc, argv, 440, 360, "img/cheby2_ap_zp_test.png", &hplot);
+  gnuplot_cmd(hplot, "unset key");
+  gnuplot_cmd(hplot, "set xzeroaxis");
+  gnuplot_cmd(hplot, "set yzeroaxis");
+  gnuplot_cmd(hplot, "set xlabel 'sigma'");
+  gnuplot_cmd(hplot, "set ylabel 'jw'");
+  gnuplot_cmd(hplot, "set size square");
+  gnuplot_cmd(hplot, "set xrange [-3:3]");
+  gnuplot_cmd(hplot, "set yrange [-3:3]");
+  gnuplot_cmd(hplot, "plot 'dat/cheby2_ap_p.txt'  with points pt 2, \\");
+  gnuplot_cmd(hplot, "     'dat/cheby2_ap_z.txt'  with points pt 6");
+  gnuplot_close(hplot); 
+
+  /* free dspl handle */
+  dspl_free(hdspl);
+
+  return res;
 }
 
-
diff --git a/examples/src/ellip_ap_zp_test.c b/examples/src/ellip_ap_zp_test.c
new file mode 100644
index 0000000..fbc7717
--- /dev/null
+++ b/examples/src/ellip_ap_zp_test.c
@@ -0,0 +1,62 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "dspl.h"
+
+/* Filter order */
+#define ORD    7
+
+int main(int argc, char* argv[])
+{
+  void* hdspl;  /* DSPL handle        */
+  void* hplot;  /* GNUPLOT handle     */
+  
+  /* Load DSPL functions */
+  hdspl = dspl_load();
+
+  complex_t z[ORD+1]; /* H(s) zeros vector */
+  complex_t p[ORD+1]; /* H(s) poles vector */
+  double Rp = 1.0;    /* Magnitude ripple from 0 to 1 rad/s */
+  double Rs = 40;     /* Stopband suppression, dB */
+
+  int res, k, nz, np;
+
+  /* Zeros and poles vectors calculation */
+  res = ellip_ap_zp(ORD, Rp,  Rs, z, &nz, p, &np);
+  if(res != RES_OK)
+    printf("error code = 0x%8x\n", res);
+
+  /* print H(s) zeros values */
+  printf("Elliptic filter zeros: %d\n", nz);
+  for(k = 0; k < nz; k++)
+    printf("z[%2d] = %9.3f %+9.3f j\n", k, RE(z[k]), IM(z[k]));
+  
+  /* print H(s) poles values */
+  printf("Elliptic filter poles: %d\n", np);
+  for(k = 0; k < np; k++)
+    printf("p[%2d] = %9.3f %+9.3f j\n", k, RE(p[k]), IM(p[k]));
+
+  /* Write complex poles to the file */
+  writetxt_cmplx(z, nz, "dat/ellip_ap_z.txt");
+  writetxt_cmplx(p, np, "dat/ellip_ap_p.txt");
+
+  /* plotting by GNUPLOT */
+  gnuplot_create(argc, argv, 440, 360, "img/ellip_ap_zp_test.png", &hplot);
+  gnuplot_cmd(hplot, "unset key");
+  gnuplot_cmd(hplot, "set xzeroaxis");
+  gnuplot_cmd(hplot, "set yzeroaxis");
+  gnuplot_cmd(hplot, "set xlabel 'sigma'");
+  gnuplot_cmd(hplot, "set ylabel 'jw'");
+  gnuplot_cmd(hplot, "set size square");
+  gnuplot_cmd(hplot, "set xrange [-2:2]");
+  gnuplot_cmd(hplot, "set yrange [-2:2]");
+  gnuplot_cmd(hplot, "plot 'dat/ellip_ap_p.txt'  with points pt 2, \\");
+  gnuplot_cmd(hplot, "     'dat/ellip_ap_z.txt'  with points pt 6");
+  gnuplot_close(hplot); 
+
+  /* free dspl handle */
+  dspl_free(hdspl);
+
+  return res;
+}
+