diff --git a/journals/models.py b/journals/models.py
index 0f833006d7d8c69b6f1337fac5f7d0474763e5f2..6acb9abe58f3680807d1526b587a6c4a54119f8c 100644
--- a/journals/models.py
+++ b/journals/models.py
@@ -2,6 +2,7 @@ from django.contrib.contenttypes.fields import GenericForeignKey
 from django.contrib.contenttypes.models import ContentType
 from django.contrib.postgres.fields import JSONField
 from django.db import models
+from django.db.models import Avg, F
 from django.utils import timezone
 from django.urls import reverse
 
@@ -51,28 +52,27 @@ class Journal(models.Model):
     def get_abbreviation_citation(self):
         return journal_name_abbrev_citation(self.name)
 
-    def nr_publications(self, Tier=None):
+    def nr_publications(self, tier=None):
         pubs = Publication.objects.filter(in_issue__in_volume__in_journal=self)
-        if Tier:
-            pubs.filter(accepted_submission__eicrecommendations__recommendation=Tier)
+        if tier:
+            pubs = pubs.filter(accepted_submission__eicrecommendations__recommendation=tier)
         return pubs.count()
 
     def avg_processing_duration(self):
         duration = Publication.objects.filter(
             in_issue__in_volume__in_journal=self).aggregate(
                 avg=Avg(F('publication_date') - F('submission_date')))['avg']
-        if not duration: return 0
-        return duration.days + duration.seconds/86400
+        return duration.total_seconds() / 86400
 
-    def citation_rate(self, Tier=None):
+    def citation_rate(self, tier=None):
         """
         Returns the citation rate in units of nr citations per article per year.
         """
         pubs = Publication.objects.filter(in_issue__in_volume__in_journal=self)
-        if Tier:
-            pubs.filter(accepted_submission__eicrecommendations__recommendation=Tier)
+        if tier:
+            pubs.filter(accepted_submission__eicrecommendations__recommendation=tier)
         ncites = 0
-        deltat = 1 # to avoid division by zero
+        deltat = 1  # to avoid division by zero
         for pub in pubs:
             if pub.citedby and pub.latest_citedby_update:
                 ncites += len(pub.citedby)
@@ -98,33 +98,32 @@ class Volume(models.Model):
     def doi_string(self):
         return '10.21468/' + self.doi_label
 
-    def nr_publications(self, Tier=None):
+    def nr_publications(self, tier=None):
         pubs = Publication.objects.filter(in_issue__in_volume=self)
-        if Tier:
-            pubs.filter(accepted_submission__eicrecommendations__recommendation=Tier)
+        if tier:
+            pubs.filter(accepted_submission__eicrecommendations__recommendation=tier)
         return pubs.count()
 
     def avg_processing_duration(self):
         duration = Publication.objects.filter(
             in_issue__in_volume=self).aggregate(
                 avg=Avg(F('publication_date') - F('submission_date')))['avg']
-        if not duration: return 0
-        return duration.days + duration.seconds/86400
+        return duration.total_seconds() / 86400
 
-    def citation_rate(self):
+    def citation_rate(self, tier=None):
         """
         Returns the citation rate in units of nr citations per article per year.
         """
         pubs = Publication.objects.filter(in_issue__in_volume=self)
-        if Tier:
-            pubs.filter(accepted_submission__eicrecommendations__recommendation=Tier)
+        if tier:
+            pubs.filter(accepted_submission__eicrecommendations__recommendation=tier)
         ncites = 0
-        deltat = 1 # to avoid division by zero
+        deltat = 1  # to avoid division by zero
         for pub in pubs:
             if pub.citedby and pub.latest_citedby_update:
                 ncites += len(pub.citedby)
                 deltat += (pub.latest_citedby_update.date() - pub.publication_date).days
-        return (ncites * 365.25/deltat)
+        return (ncites * 365.25 / deltat)
 
 
 class Issue(models.Model):
@@ -177,29 +176,28 @@ class Issue(models.Model):
         return self.start_date <= timezone.now().date() and\
                self.until_date >= timezone.now().date()
 
-    def nr_publications(self, Tier=None):
-        pubs = Publication.objects.filter(in_issue=self)
-        if Tier:
-            pubs.filter(accepted_submission__eicrecommendations__recommendation=Tier)
-        return pubs.count()
+    def nr_publications(self, tier=None):
+        publications = Publication.objects.filter(in_issue=self)
+        if tier:
+            publications.filter(accepted_submission__eicrecommendations__recommendation=tier)
+        return publications.count()
 
     def avg_processing_duration(self):
         duration = Publication.objects.filter(
             in_issue=self).aggregate(
                 avg=Avg(F('publication_date') - F('submission_date')))['avg']
-        if not duration: return 0
-        return duration.days + duration.seconds/86400
+        return duration.total_seconds() / 86400
 
-    def citation_rate(self, Tier=None):
+    def citation_rate(self, tier=None):
         """
         Returns the citation rate in units of nr citations per article per year.
         """
-        pubs = Publication.objects.filter(in_issue=self)
-        if Tier:
-            pubs.filter(accepted_submission__eicrecommendations__recommendation=Tier)
+        publications = Publication.objects.filter(in_issue=self)
+        if tier:
+            publications.filter(accepted_submission__eicrecommendations__recommendation=tier)
         ncites = 0
-        deltat = 1 # to avoid division by zero
-        for pub in pubs:
+        deltat = 1  # to avoid division by zero
+        for pub in publications:
             if pub.citedby and pub.latest_citedby_update:
                 ncites += len(pub.citedby)
                 deltat += (pub.latest_citedby_update.date() - pub.publication_date).days
diff --git a/stats/templates/stats/statistics.html b/stats/templates/stats/statistics.html
index 3f02a39811badcda9e139b5828cdd8885e5066d3..7e7b6a7285487e28646c470e953f785e9bcb60a9 100644
--- a/stats/templates/stats/statistics.html
+++ b/stats/templates/stats/statistics.html
@@ -107,28 +107,28 @@
   <tr>
     {% if issue %}
     <td>{% issue.doi_label }}</td>
-    <td>{% nr_publications issue Tier=1 %}</td>
-    <td>{% nr_publications issue Tier=2 %}</td>
-    <td>{% nr_publications issue Tier=3 %}</td>
-    <td>{% citation_rate issue Tier=1 as cr %}{{ cr|floatformat:2 }}</td>
-    <td>{% citation_rate issue Tier=2 as cr %}{{ cr|floatformat:2 }}</td>
-    <td>{% citation_rate issue Tier=3 as cr %}{{ cr|floatformat:2 }}</td>
+    <td>{% nr_publications issue tier=1 %}</td>
+    <td>{% nr_publications issue tier=2 %}</td>
+    <td>{% nr_publications issue tier=3 %}</td>
+    <td>{% citation_rate issue tier=1 as cr %}{{ cr|floatformat:2 }}</td>
+    <td>{% citation_rate issue tier=2 as cr %}{{ cr|floatformat:2 }}</td>
+    <td>{% citation_rate issue tier=3 as cr %}{{ cr|floatformat:2 }}</td>
     {% elif volume %}
     <td>{{ volume.doi_label }}</td>
-    <td>{% nr_publications volume Tier=1 %}</td>
-    <td>{% nr_publications volume Tier=2 %}</td>
-    <td>{% nr_publications volume Tier=3 %}</td>
-    <td>{% citation_rate volume Tier=1 as cr %}{{ cr|floatformat:2 }}</td>
-    <td>{% citation_rate volume Tier=2 as cr %}{{ cr|floatformat:2 }}</td>
-    <td>{% citation_rate volume Tier=3 as cr %}{{ cr|floatformat:2 }}</td>
+    <td>{% nr_publications volume tier=1 %}</td>
+    <td>{% nr_publications volume tier=2 %}</td>
+    <td>{% nr_publications volume tier=3 %}</td>
+    <td>{% citation_rate volume tier=1 as cr %}{{ cr|floatformat:2 }}</td>
+    <td>{% citation_rate volume tier=2 as cr %}{{ cr|floatformat:2 }}</td>
+    <td>{% citation_rate volume tier=3 as cr %}{{ cr|floatformat:2 }}</td>
     {% else %}
     <td>{{ journal.doi_label }}</td>
-    <td>{% nr_publications journal Tier=1 %}</td>
-    <td>{% nr_publications journal Tier=2 %}</td>
-    <td>{% nr_publications journal Tier=3 %}</td>
-    <td>{% citation_rate journal Tier=1 as cr %}{{ cr|floatformat:2 }}</td>
-    <td>{% citation_rate journal Tier=2 as cr %}{{ cr|floatformat:2 }}</td>
-    <td>{% citation_rate journal Tier=3 as cr %}{{ cr|floatformat:2 }}</td>
+    <td>{% nr_publications journal tier=1 %}</td>
+    <td>{% nr_publications journal tier=2 %}</td>
+    <td>{% nr_publications journal tier=3 %}</td>
+    <td>{% citation_rate journal tier=1 as cr %}{{ cr|floatformat:2 }}</td>
+    <td>{% citation_rate journal tier=2 as cr %}{{ cr|floatformat:2 }}</td>
+    <td>{% citation_rate journal tier=3 as cr %}{{ cr|floatformat:2 }}</td>
     {% endif %}
   </tr>
 </table>
diff --git a/stats/templatetags/stats_extras.py b/stats/templatetags/stats_extras.py
index fb0b8cdf2048b6562b2d9e82258117b021db2f64..335c813cc216907cb5ee9828390e200a42969854 100644
--- a/stats/templatetags/stats_extras.py
+++ b/stats/templatetags/stats_extras.py
@@ -1,28 +1,21 @@
 from django import template
-from django.db.models import Avg, F
-
-from journals.models import Publication
-from submissions.constants import SUBMISSION_STATUS_OUT_OF_POOL
-from submissions.models import Submission
 
 register = template.Library()
 
 
-
 @register.simple_tag
 def avg_processing_duration(obj, *args, **kwargs):
-    method = getattr(obj, avg_processing_duration)
-    return method(*args, **kwargs)
+    return getattr(obj, 'avg_processing_duration')(*args, **kwargs)
+
 
 @register.simple_tag
 def nr_publications(obj, *args, **kwargs):
-    method = getattr(obj, nr_publications)
-    return method(*args, **kwargs)
+    return getattr(obj, 'nr_publications')(*args, **kwargs)
+
 
 @register.simple_tag
 def citation_rate(obj, *args, **kwargs):
-    method = getattr(obj, citation_rate)
-    return method(*args, **kwargs)
+    return getattr(obj, 'citation_rate')(*args, **kwargs)
 
 
 @register.filter(name='submissions_count_distinct')
diff --git a/stats/views.py b/stats/views.py
index 11d7bd845e11df31b0c12fc591974163be366f78..dd416c843a34dfa75973cb963d437ddbd601ba5e 100644
--- a/stats/views.py
+++ b/stats/views.py
@@ -1,10 +1,9 @@
 import datetime
 
-from django.contrib.auth.decorators import login_required, permission_required
+from django.contrib.auth.decorators import permission_required
 from django.shortcuts import get_object_or_404, render
 
-from journals.constants import SCIPOST_JOURNALS_SUBMIT
-from journals.models import Journal, Volume, Issue, Publication
+from journals.models import Journal, Volume, Issue
 from submissions.models import Submission
 
 
@@ -19,8 +18,9 @@ def statistics(request, journal_doi_label=None, volume_nr=None, issue_nr=None, y
         context['journal'] = journal
         if year:
             context['year'] = year
-            submissions = Submission.objects.filter(submitted_to_journal=journal_doi_label
-            ).originally_submitted(datetime.date(int(year), 1, 1), datetime.date(int(year), 12, 31))
+            submissions = Submission.objects.filter(
+                submitted_to_journal=journal_doi_label).originally_submitted(
+                datetime.date(int(year), 1, 1), datetime.date(int(year), 12, 31))
             context['submissions'] = submissions
             nr_ref_inv = 0
             nr_acc = 0
@@ -29,8 +29,6 @@ def statistics(request, journal_doi_label=None, volume_nr=None, issue_nr=None, y
             nr_rep_obt = 0
             nr_rep_obt_inv = 0
             nr_rep_obt_con = 0
-            nr_rep_ref = 0
-            nr_aw_vet = 0
             for submission in submissions:
                 nr_ref_inv += submission.referee_invitations.count()
                 nr_acc += submission.count_accepted_invitations()