added acknowledgements

src/main/java/UserInterface.java

@@ -25,7 +25,7 @@ public class UserInterface {
                     case 1 -> makeCells();
                     case 2 -> makePlate();
                     case 3 -> matchCells();
-                    //case 4 -> //method call goes here
+                    case 4 -> acknowledge();
                     case 0 -> quit = true;
                     default -> throw new InputMismatchException("Invalid input.");
                 }
@@ -189,4 +189,13 @@ public class UserInterface {
             Simulator.matchCells(filename, cells, plate, lowThreshold, highThreshold);
         }
     }
+
+    private static void acknowledge(){
+        System.out.println("Simulation based on:");
+        System.out.println("Howie, B., Sherwood, A. M., et. al.");
+        System.out.println("High-throughput pairing of T cell receptor alpha and beta sequences.");
+        System.out.println("Sci. Transl. Med. 7, 301ra131 (2015)");
+        System.out.println("");
+        System.out.println("Simulation by Eugene Fischer, 2021");
+    }
 }