diff --git a/MainWindow.xaml.cs b/MainWindow.xaml.cs
index 9fe73fc..a4c8fe1 100644
--- a/MainWindow.xaml.cs
+++ b/MainWindow.xaml.cs
@@ -55,7 +55,7 @@ namespace Txt2Bib
             if (dataObject.ContainsFileDropList())
             {
                 // Clear values
-                DropArea.Text = string.Empty;
+                if (DropArea.Text == InitialDropText) DropArea.Text = string.Empty;
 
                 // Process file names
                 var fileNames = dataObject.GetFileDropList();
@@ -65,7 +65,7 @@ namespace Txt2Bib
                     bd.Append(fileName + "\n");
                 }
                 // Set text
-                DropArea.Text = bd.ToString();
+                DropArea.Text += bd.ToString();
             }
         }
 
diff --git a/Text2Bib.cs b/Text2Bib.cs
index 9cb163d..3e3e1fc 100644
--- a/Text2Bib.cs
+++ b/Text2Bib.cs
@@ -15,7 +15,7 @@ namespace Txt2Bib
     /// </summary>
     public class Text2Bib
     {
-        private string[] _citTypes = { "J", "B", "C", "P" };
+        private readonly string[] _citTypes = { "J", "B", "C", "P" };
         
         /// <summary>
         /// Generate single .bib file from input text files
diff --git a/Txt2Bib.csproj b/Txt2Bib.csproj
index bc2cd8b..ef42879 100644
--- a/Txt2Bib.csproj
+++ b/Txt2Bib.csproj
@@ -5,7 +5,7 @@
     <TargetFramework>net6.0-windows</TargetFramework>
     <Nullable>enable</Nullable>
     <UseWPF>true</UseWPF>
-    <Version>0.1.2</Version>
+    <Version>0.1.4</Version>
   </PropertyGroup>
 
   <ItemGroup>