diff --git a/ex-4_35-xx.scm b/ex-4_35-xx.scm
index 7fcd75b..0642bcb 100644
--- a/ex-4_35-xx.scm
+++ b/ex-4_35-xx.scm
@@ -214,9 +214,55 @@
 (my-assert (multiple-dwelling)
            (car (multiple-dwelling-ordinary)))
 
-(display "\nex-4.42\n")
+(display "\nex-4.42 - liars-puzzle\n")
 
-(display "\nex-4.43\n")
+(define (no-violation new-stmt stmts)
+  (if (null? stmts)
+    #t
+    (let ((stmt (car stmts)))
+      (cond
+        ((and (eq? (car new-stmt) (car stmt))
+              (not (eq? (cadr new-stmt) (cadr stmt)))) #f)
+        ((and (not (eq? (car new-stmt) (car stmt)))
+              (eq? (cadr new-stmt) (cadr stmt))) #f)
+        (else (no-violation new-stmt (cdr stmts)))))))
+
+(define (liars-puzzle-1)
+  (let ((stmt-1 (amb '(kitty 2) '(betty 3))))
+    (require (no-violation stmt-1 '()))
+    (let ((stmt-2 (amb '(ethel 1) '(joan 2))))
+      (require (no-violation stmt-2 (list stmt-1)))
+      (let ((stmt-3 (amb '(joan 3) '(ethel 5))))
+        (require (no-violation stmt-3 (list stmt-1 stmt-2)))
+        (let ((stmt-4 (amb '(kitty 2) '(mary 4))))
+          (require (no-violation stmt-4 (list stmt-1 stmt-2 stmt-3)))
+          (let ((stmt-5 (amb '(mary 4) '(betty 1))))
+            (require (no-violation stmt-5 (list stmt-1 stmt-2 stmt-3 stmt-4)))
+            (list stmt-1 stmt-2 stmt-3 stmt-4 stmt-5)))))))
+
+(define (liars-puzzle statements solution)
+  (if (null? statements)
+    solution
+    (let ((stmt ((car statements))))
+      (require (no-violation stmt solution))
+      (liars-puzzle (cdr statements) (append solution (list stmt))))))
+
+(define statements (list
+                     (lambda () (amb '(kitty 2) '(betty 3)))
+                     (lambda () (amb '(ethel 1) '(joan 2)))
+                     (lambda () (amb '(joan 3) '(ethel 5)))
+                     (lambda () (amb '(kitty 2) '(mary 4)))
+                     (lambda () (amb '(mary 4) '(betty 1)))))
+
+(my-assert (liars-puzzle-1) (liars-puzzle statements '()))
+
+; Two implementations of the same algorithm. Note that the solution does not
+; show the position of all students. It only provides a subset of states that
+; do no result in a violation. We would have to do some further computations on
+; that result to get the position of each individual student.
+
+
+(display "\nex-4.43 - lornas-father\n")
 
 ; (display "\nex-4.44 - eight-queens\n")