diff --git a/gnssanalysis/gn_diffaux.py b/gnssanalysis/gn_diffaux.py
index a90a116..1240d17 100644
--- a/gnssanalysis/gn_diffaux.py
+++ b/gnssanalysis/gn_diffaux.py
@@ -472,7 +472,7 @@ def sisre(
         _logging.info(msg="plotting RAC difference")
         _gn_plot.racplot(rac_unstack=rac_unstack, output=plot if isinstance(plot, str) else None)
 
-    if (clk_a is not None) & (clk_b is not None):  # check if clk data is present
+    if (clk_test is not None) and (clk_baseline is not None):  # check if clk data is present
         clk_diff = (
             compare_clk(
                 clk_a, clk_b, norm_types=norm_types, ext_dt=rac_unstack.index, ext_svs=rac_unstack.columns.levels[1]
diff --git a/gnssanalysis/gn_io/sinex.py b/gnssanalysis/gn_io/sinex.py
index 1100c72..ce22c9a 100644
--- a/gnssanalysis/gn_io/sinex.py
+++ b/gnssanalysis/gn_io/sinex.py
@@ -845,7 +845,7 @@ def llh2snxdms(llh):
     ll_stack = _pd.concat([llh_degminsec_df.LON, llh_degminsec_df.LAT], axis=0)
     ll_stack = ll_stack.D.str.rjust(4).values + ll_stack.M.str.rjust(3).values + ll_stack.S.str.rjust(5).values
     buf = ll_stack[:n_rows] + ll_stack[n_rows:] + llh_degminsec_df.HEI.str.rjust(8).values
-
+    # The following is a Numpy OR operator (not a standard Python bitwise OR):
     buf[(height > 8000) | (height < -2000)] = " 000 00 00.0  00 00 00.0   000.0"  # | zero_mask
     return buf
 
diff --git a/gnssanalysis/gn_utils.py b/gnssanalysis/gn_utils.py
index bd76cb0..f46029f 100644
--- a/gnssanalysis/gn_utils.py
+++ b/gnssanalysis/gn_utils.py
@@ -467,7 +467,7 @@ def log2snx(logglob, rnxglob, outfile, frame_snx, frame_dis, frame_psd, datetime
     from .gn_io import igslog
 
     if isinstance(rnxglob, list):
-        if (len(rnxglob) == 1) & (
+        if (len(rnxglob) == 1) and (
             rnxglob[0].find("*") != -1
         ):  # it's rnx_glob expression (may be better to check if star is present)
             rnxglob = rnxglob[0]