diff --git a/M6502/M6502.Symbols/IdentifiableSection.cs b/M6502/M6502.Symbols/IdentifiableSection.cs
index f128b9c..efdf15d 100644
--- a/M6502/M6502.Symbols/IdentifiableSection.cs
+++ b/M6502/M6502.Symbols/IdentifiableSection.cs
@@ -1,6 +1,7 @@
 namespace M6502.Symbols
 {
     using System.Collections;
+    using System.Collections.ObjectModel;
     using System.Diagnostics;
 
     public class IdentifiableSection : Section
@@ -14,8 +15,8 @@
 
         private bool MaybeExtractFromParsed(string key, out string? value)
         {
-            Debug.Assert(this._parsed is not null);
-            var found = this._parsed.TryGetValue(key, out var extracted);
+            Debug.Assert(this.Parsed is not null);
+            var found = this.Parsed.TryGetValue(key, out var extracted);
             value = extracted;
             return found;
         }
@@ -27,10 +28,10 @@
             return available;
         }
 
-        protected bool MaybeExtractCompoundInteger(string key, out List<int> value)
+        protected bool MaybeExtractCompoundInteger(string key, out ReadOnlyCollection<int> value)
         {
             var available = this.MaybeExtractFromParsed(key, out var extracted);
-            value = extracted is null ? [] : ExtractCompoundInteger(extracted);
+            value = extracted is null ? new ReadOnlyCollection<int>([]) : ExtractCompoundInteger(extracted);
             return available;
         }
 
@@ -70,11 +71,11 @@
             var referencingContainer = referenceClassAttribute.Referencing;
 
             // Get the parent container field
-            var containerType = this._container.GetType();
+            var containerType = this.Container.GetType();
             Debug.Assert(referencingContainer is not null);
             var containerField = containerType.GetField(referencingContainer);
             Debug.Assert(containerField is not null);
-            var fieldValue = containerField.GetValue(this._container);
+            var fieldValue = containerField.GetValue(this.Container);
             var fieldList = fieldValue as IList;
 
             // Now get the referenced object from the parent container field (via ID as an index)
@@ -100,7 +101,7 @@
             }
         }
 
-        private void ExtractReferencesProperty(List<int> ids, string name, System.Type type)
+        private void ExtractReferencesProperty(ReadOnlyCollection<int> ids, string name, System.Type type)
         {
             // The reference container in the parent class
             //var referenceSectionProperties = GetSectionProperties(type);
diff --git a/M6502/M6502.Symbols/Section.cs b/M6502/M6502.Symbols/Section.cs
index 07ebc6b..33eeb9e 100644
--- a/M6502/M6502.Symbols/Section.cs
+++ b/M6502/M6502.Symbols/Section.cs
@@ -1,6 +1,7 @@
 namespace M6502.Symbols
 {
     using System;
+    using System.Collections.ObjectModel;
     using System.Diagnostics;
     using System.Globalization;
     using System.Numerics;
@@ -11,13 +12,15 @@
         protected static readonly Dictionary<System.Type, ReflectedSectionProperties> SectionPropertiesCache = [];
         protected static readonly DateTime UnixEpoch = new(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);
 
-        protected readonly Parser _container;
+        private readonly Parser _container;
 
         // Needed to evaluate references on a second pass
-        protected readonly Dictionary<string, int> _references = [];
-        protected readonly Dictionary<string, List<int>> _multipleReferences = [];
+        private readonly Dictionary<string, int> _references = [];
+        private readonly Dictionary<string, List<int>> _multipleReferences = [];
 
-        protected Dictionary<string, string>? _parsed;
+        protected Parser Container => this._container;
+
+        protected Dictionary<string, string>? Parsed { get; private set; }
 
         protected ReflectedSectionProperties SectionProperties => GetSectionProperties(this.GetType());
 
@@ -48,7 +51,7 @@
         public virtual void Parse(Dictionary<string, string>? entries)
         {
             ArgumentNullException.ThrowIfNull(entries);
-            this._parsed = entries;
+            this.Parsed = entries;
             this._container.SectionEntries.Add(this);
             this.ProcessAttributesOfProperties();
             foreach (var entry in entries)
@@ -84,7 +87,8 @@
                 }
                 else if (references)
                 {
-                    this._multipleReferences.Add(key, ExtractCompoundInteger(value));
+                    var multiple = ExtractCompoundInteger(value);
+                    this._multipleReferences.Add(key, [.. multiple]);
                 }
                 else
                 {
@@ -154,7 +158,7 @@
             return value.Split('+');
         }
 
-        protected static List<int> ExtractCompoundInteger(string value)
+        protected static ReadOnlyCollection<int> ExtractCompoundInteger(string value)
         {
             var elements = ExtractCompoundString(value);
             var returned = new List<int>(elements.Length);
@@ -162,7 +166,7 @@
             {
                 returned.Add(ExtractInteger(element));
             }
-            return returned;
+            return returned.AsReadOnly();
         }
     }
 }
\ No newline at end of file