diff --git a/app/views/samples/_spectrum_panel.html.erb b/app/views/samples/_spectrum_panel.html.erb
index 0b7828d..7a2b3e8 100644
--- a/app/views/samples/_spectrum_panel.html.erb
+++ b/app/views/samples/_spectrum_panel.html.erb
@@ -6,21 +6,21 @@
         <path d="M8 4h-3v16h3"></path>
         <path d="M16 4h3v16h-3"></path>
       </svg>
-      <div class="flex space-x-1 text-gray-700">
-        <span class="my-auto">
-          <%= ApplicationHelper.humanize_range spectrum.range %>
+      <div class="flex text-gray-700">
+        <span class="my-auto mr-2 text-sm font-medium text-gray-500">
+          <%= ApplicationHelper.humanize_category spectrum.category %>
         </span>
-        <div class="my-auto">
+        <div class="my-auto mr-2 text-sm text-gray-500">
           &middot;
         </div>
-        <span class="my-auto">
-          <%= ApplicationHelper.humanize_category spectrum.category %>
+        <span class="my-auto mr-2 text-xs font-medium text-gray-500">
+          <%= ApplicationHelper.humanize_file_format spectrum.format %>
         </span>
-        <div class="my-auto">
+        <div class="my-auto mr-2 text-sm text-gray-500">
           &middot;
         </div>
-        <span class="my-auto">
-          <%= ApplicationHelper.humanize_file_format spectrum.format %>
+        <span class="my-auto mr-2 text-xs font-medium text-gray-500">
+          id: <%= spectrum.id %>
         </span>
       </div>
     </div>
diff --git a/app/views/samples/show.html.erb b/app/views/samples/show.html.erb
index e31fef6..41646ef 100644
--- a/app/views/samples/show.html.erb
+++ b/app/views/samples/show.html.erb
@@ -59,6 +59,19 @@
                             <%= spectrum.file.filename.to_s.truncate(20) %>
                           </span>
                         </div>
+                        <% if spectrum.is_reference? %>
+                          <div class="my-auto">
+                            <%= render TooltipComponent.new(tooltip: "Reference", user: current_user) do %>
+                              <svg xmlns="http://www.w3.org/2000/svg" class="icon icon-tabler icon-tabler-box w-4 h-4" width="24" height="24" viewBox="0 0 24 24" stroke-width="2" stroke="currentColor" fill="none" stroke-linecap="round" stroke-linejoin="round">
+                                <path stroke="none" d="M0 0h24v24H0z" fill="none"></path>
+                                <path d="M12 3l8 4.5l0 9l-8 4.5l-8 -4.5l0 -9l8 -4.5"></path>
+                                <path d="M12 12l8 -4.5"></path>
+                                <path d="M12 12l0 9"></path>
+                                <path d="M12 12l-8 -4.5"></path>
+                              </svg>
+                            <% end %>
+                          </div>
+                        <% end %>
                       </div>
                     <% end %>
                   </li>
diff --git a/app/views/spectra/edit.html.erb b/app/views/spectra/edit.html.erb
index 6274a70..7ffd4bc 100644
--- a/app/views/spectra/edit.html.erb
+++ b/app/views/spectra/edit.html.erb
@@ -24,6 +24,16 @@
                 <%= f.input :category, default: @spectrum.category, collection: SpectraHelper::HUMANIZED_CATEGORIES_COLLECTION, input_html: { class: "w-full p-4 pr-6 text-sm border-gray-300 rounded-md shadow-sm focus:ring-1 focus:ring-primary-500 focus:border-primary-600 peer" }, hint: false, label: false %>
               </div>
 
+              <div>
+                <%= render Forms::LabelComponent.new(optional: true).with_content("Sample thickness (mm)") %>
+                <%= f.input :sample_thickness, as: :float, input_html: { class: "w-full p-4 pr-6 text-sm border-gray-300 rounded-md shadow-sm focus:ring-1 focus:ring-primary-500 focus:border-primary-600", min: 0, step: 0.1 }, error_html: { data: { controller: 'flash', 'flash-target': 'flash' } }, placeholder: "3.61", required: false, disabled: false, readonly: false, hint: false, label: false, error: false %>
+              </div>
+
+              <div class="flex my-auto space-x-2">
+                <%= f.input :is_reference, default: false, input_html: { class: "w-4 h-4 text-primary-600 bg-gray-100 border-gray-300 rounded focus:ring-primary-500" } %>
+                <%= render Forms::LabelComponent.new(optional: true, cls: "!mb-0").with_content("Reference spectrum") %>
+              </div>
+
               <div class="col-span-2 mb-4">
                 <%= render Forms::LabelComponent.new().with_content("Description") %>
                 <%= render Forms::TextInputComponent.new(form: f, as: :rich_text_area, field: :description, required: false, placeholder: "General description") %>
diff --git a/app/views/spectra/new.html.erb b/app/views/spectra/new.html.erb
index 0e79d9a..8360520 100644
--- a/app/views/spectra/new.html.erb
+++ b/app/views/spectra/new.html.erb
@@ -24,6 +24,16 @@
                 <%= f.input :category, default: @spectrum.category, collection: SpectraHelper::HUMANIZED_CATEGORIES_COLLECTION, input_html: { class: "w-full p-4 pr-6 text-sm border-gray-300 rounded-md shadow-sm focus:ring-1 focus:ring-primary-500 focus:border-primary-600 peer" }, hint: false, label: false %>
               </div>
 
+              <div>
+                <%= render Forms::LabelComponent.new(optional: true).with_content("Sample thickness (mm)") %>
+                <%= f.input :sample_thickness, as: :float, input_html: { class: "w-full p-4 pr-6 text-sm border-gray-300 rounded-md shadow-sm focus:ring-1 focus:ring-primary-500 focus:border-primary-600", min: 0.1, step: 0.1 }, error_html: { data: { controller: 'flash', 'flash-target': 'flash' } }, placeholder: "3.61", required: false, disabled: false, readonly: false, hint: false, label: false, error: false %>
+              </div>
+
+              <div class="flex my-auto space-x-2">
+                <%= f.input :is_reference, default: false, input_html: { class: "w-4 h-4 text-primary-600 bg-gray-100 border-gray-300 rounded focus:ring-primary-500" } %>
+                <%= render Forms::LabelComponent.new(optional: true, cls: "!mb-0").with_content("Reference spectrum") %>
+              </div>
+
               <div class="col-span-2 mb-4">
                 <%= render Forms::LabelComponent.new().with_content("Description") %>
                 <%= render Forms::TextInputComponent.new(form: f, as: :rich_text_area, field: :description, required: false, placeholder: "General description") %>