diff --git a/kenzo-test.asd b/kenzo-test.asd
index db46d5a..8bfe181 100644
--- a/kenzo-test.asd
+++ b/kenzo-test.asd
@@ -22,6 +22,7 @@
 	       (:file "cobar-test")
 	       (:file "combinations-test")
 	       (:file "cones-test")
+	       (:file "cs-twisted-products-test")
 	       (:file "delta-test")
 	       (:file "diabolo")
 	       (:file "effective-homology-test")
diff --git a/package.lisp b/package.lisp
index c8137d5..74bfa5c 100644
--- a/package.lisp
+++ b/package.lisp
@@ -214,6 +214,11 @@
 	   TERM-CON1
 	   TERM-UNCON
 
+	   ;; cs-twisted-products.lisp
+
+	   SMGR-CRTS-CONTRACTION
+	   SMGR-FIBRATION
+	   SMGR-TNPR-CONTRACTION
 
 	   ;; delta.lisp
 
@@ -344,6 +349,10 @@
 
 	   HOMOLOGY
 
+	   ;; serre.lisp
+
+	   BROWN-REDUCTION
+
 	   ;; simplicial-mrphs.lisp
 
 	   BUILD-SMMR
diff --git a/src/cs-twisted-products.lisp b/src/cs-twisted-products.lisp
index 6909459..ac2393c 100644
--- a/src/cs-twisted-products.lisp
+++ b/src/cs-twisted-products.lisp
@@ -8,139 +8,69 @@
 
 (DEFUN SMGR-FIBRATION-SINTR (dmns gbar)
   (declare
-    (ignore dmns)
-    (type gbar gbar))
+   (ignore dmns)
+   (type gbar gbar))
   (the absm
-    (first (gbar-list gbar))))
+       (first (gbar-list gbar))))
 
 (DEFUN SMGR-FIBRATION (smgr)
   (declare (type simplicial-group smgr))
   (the fibration
-    (build-smmr
-      :sorc (classifying-space smgr)
-      :trgt smgr
-      :degr -1
-      :sintr #'smgr-fibration-sintr
-      :orgn `(simplicial-group-fibration ,smgr))))
+       (build-smmr
+	:sorc (classifying-space smgr)
+	:trgt smgr
+	:degr -1
+	:sintr #'smgr-fibration-sintr
+	:orgn `(simplicial-group-fibration ,smgr))))
 
-#|
-  (setf k1 (k-z-1))
-  (setf tw (smgr-fibration k1))
-  (setf k2 (sorc tw))
-  (setf tt (fibration-total tw))
-  (setf gmsm (crpr 0 (gbar 4 0 '(10 11 12) 0 '(20 21) 0 '(30) 0 '())
-                   0 '(2 4 6 8)))
-  (dotimes (i 5)
-    (print (face tt i 4 gmsm)))
-  (setf br (brown-reduction tw))
-  (setf tw-pr (bcc br))
-  (? tw-pr 4 (tnpr 4 (gbar 4 0 '(1 10 100) 0 '(1000 10000)
-                             0 '(100000) 0 '())
-                   0 '()))
-|#
 
 (DEFUN SMGR-CRTS-CONTRACTION-INTR (idnt)
   (declare
-    (type gmsm idnt))
+   (type gmsm idnt))
   (flet ((rslt (degr crpr
 		     &aux (degr+1 (1+ degr)))
 	   (declare
 	    (fixnum degr degr+1)
 	    (type crpr crpr))
 	   (the cmbn
-	     (with-crpr (absm1 absm2) crpr
-	       (if (= (dgop absm2) (mask degr))
-		 (zero-cmbn degr+1)
-		 (term-cmbn degr+1
-		   (-1-expt-n+1 degr)
-		   (crpr 0 (make-gbar
-			    :dmns degr+1
-			    :list (cons absm2
-					(rest (unnormalize-gbar absm1 idnt))))
-			 (mask degr+1) idnt)))))))
-     (the intr-mrph #'rslt)))
+		(with-crpr
+		    (absm1 absm2) crpr
+		    (if (= (dgop absm2) (mask degr))
+			(zero-cmbn degr+1)
+			(term-cmbn degr+1
+				   (-1-expt-n+1 degr)
+				   (crpr 0 (make-gbar
+					    :dmns degr+1
+					    :list (cons absm2
+							(rest
+							 (unnormalize-gbar
+							  absm1 idnt))))
+					 (mask degr+1) idnt)))))))
+    (the intr-mrph #'rslt)))
+
 
 (DEFUN SMGR-CRTS-CONTRACTION (smgr)
   (declare (type simplicial-group smgr))
   (the morphism
-    (build-mrph
-      :sorc (fibration-total (smgr-fibration smgr))
-      :trgt (fibration-total (smgr-fibration smgr))
-      :degr +1
-      :intr (smgr-crts-contraction-intr (bspn smgr))
-      :strt :gnrt
-      :orgn `(smgr-crts-contraction ,smgr))))
+       (build-mrph
+	:sorc (fibration-total (smgr-fibration smgr))
+	:trgt (fibration-total (smgr-fibration smgr))
+	:degr +1
+	:intr (smgr-crts-contraction-intr (bspn smgr))
+	:strt :gnrt
+	:orgn `(smgr-crts-contraction ,smgr))))
 
-#|
-  (cat-init)
-  (setf chi (smgr-crts-contraction (k-z-1)))
-  (setf rdct (build-rdct :f (zero-mrph (sorc chi) (z-chcm))
-                         :g (zero-mrph (z-chcm) (sorc chi))
-                         :h chi))
-  (pre-check-rdct rdct)
-  (setf *tc* (cmbn 0 1 (crpr 0 +null-gbar+ 0 '())))
-  (setf *bc* (cmbn 0 1 :z-gnrt))
-  (check-rdct)
-  (setf *tc* (cmbn 1 1 (crpr 1 +null-gbar+ 0 '(1))))
-  (check-rdct)
-  (setf *tc* (cmbn 4 1 (crpr 0 (gbar 4 0 '(10 11 12) 0 '(20 21) 0 '(30) 0 '())
-                             0 '(2 4 6 8))))
-  (check-rdct)
-  (setf *tc* (cmbn 3 1 (crpr 0 (gbar 3 0 '(10 11) 0 '(20) 0 '())
-                             0 '(2 4 6))))
-  (check-rdct)
-|#
 
 (DEFUN SMGR-TNPR-CONTRACTION (smgr
-			        &aux (fibration (smgr-fibration smgr))
-				     (brown (brown-reduction fibration))
-				     (f (f brown))
-				     (g (g brown))
-				     (chi (smgr-crts-contraction smgr)))
+			      &aux (fibration (smgr-fibration smgr))
+				(brown (brown-reduction fibration))
+				(f (f brown))
+				(g (g brown))
+				(chi (smgr-crts-contraction smgr)))
   (declare
-    (type simplicial-group smgr)
-    (type fibration fibration)
-    (type reduction brown)
-    (type morphism f g chi))
+   (type simplicial-group smgr)
+   (type fibration fibration)
+   (type reduction brown)
+   (type morphism f g chi))
   (the morphism
-    (i-cmps f chi g)))
-
-#|
-  (cat-init)
-  (setf chi (smgr-tnpr-contraction (k-z-1)))
-  (setf rdct (build-rdct :f (zero-mrph (sorc chi) (z-chcm))
-                         :g (zero-mrph (z-chcm) (sorc chi))
-                         :h chi))
-  (pre-check-rdct rdct)
-  (setf *tc* (cmbn 0 1 (tnpr 0 +null-gbar+ 0 '())))
-  (setf *bc* (cmbn 0 1 :z-gnrt))
-  (check-rdct)
-  (setf *tc* (cmbn 1 1 (tnpr 0 +null-gbar+ 1 '(1))))
-  (check-rdct)
-  (setf *tc* (cmbn 3 1 (tnpr 0 +null-gbar+ 3 '(1 10 100))))
-  (? chi *tc*)
-  (check-rdct)
-  (setf *tc* (cmbn 3 1 (tnpr 2 (gbar 2 0 '(1) 0 '()) 1 '(10))))
-  (? chi *tc*)
-  (check-rdct)
-  (setf *tc* (cmbn 3 1 (tnpr 3 (gbar 3 0 '(1 10) 0 '(100) 0 '()) 0 '())))
-  (? chi *tc*)
-  (check-rdct)
-  (setf *tc* (cmbn 4 1 (tnpr 0 +null-gbar+ 4 '(1 10 100 1000))))
-  (? chi *tc*)
-  (check-rdct)
-  (setf *tc* (cmbn 4 1 (tnpr 2 (gbar 2 0 '(1) 0 '()) 2 '(10 100))))
-  (? chi *tc*)
-  (check-rdct)
-  (setf *tc* (cmbn 4 1 (tnpr 3 (gbar 3 0 '(1 10) 0 '(100) 0 '())
-                             1 '(1000))))
-  (? chi *tc*)
-  (check-rdct)
-  (setf *tc* (cmbn 4 1 (tnpr 4 (gbar 4 0 '(1 10 100)
-                                       0 '(1000 10000)
-                                       0 '(100000)
-                                       0 '())
-                              0 '())))
-  (? chi *tc*)
-  (check-rdct)
-|#
+       (i-cmps f chi g)))
diff --git a/test/cs-twisted-products-test.lisp b/test/cs-twisted-products-test.lisp
new file mode 100644
index 0000000..95ddac8
--- /dev/null
+++ b/test/cs-twisted-products-test.lisp
@@ -0,0 +1,97 @@
+
+(in-package :kenzo-test)
+
+(in-suite :kenzo)
+
+(test smgr-fibration
+      (cat:cat-init)
+      (let* ((k1 (cat:k-z-1))
+	     (tw (cat:smgr-fibration k1))
+	     (k2 (cat:sorc tw))
+	     (tt (cat:fibration-total tw))
+	     (gmsm (cat:crpr 0 (cat:gbar 4 0 '(10 11 12) 0 '(20 21)
+					 0 '(30) 0 '())
+			     0 '(2 4 6 8)))
+	     (br (cat:brown-reduction tw))
+	     (tw-pr (cat:bcc br)))
+	(dotimes (i 5)
+	  (print (cat:face tt i 4 gmsm)))
+	(cat:? tw-pr 4 (cat:tnpr 4 (cat:gbar 4 0 '(1 10 100) 0 '(1000 10000)
+					     0 '(100000) 0 '())
+				 0 '()))))
+
+#|
+(test smgr-crts-contraction
+      (cat:cat-init)
+      (let* ((chi (cat:smgr-crts-contraction (cat:k-z-1)))
+	     (rdct (cat:build-rdct :f (cat:zero-mrph (cat:sorc chi)
+						     (cat:z-chcm))
+				   :g (cat:zero-mrph (cat:z-chcm)
+						     (cat:sorc chi))
+				   :h chi)))
+	(cat:pre-check-rdct rdct)
+	(setf cat:*tc* (cat:cmbn 0 1 (cat:crpr 0 cat:+null-gbar+ 0 '())))
+	(setf cat:*bc* (cat:cmbn 0 1 :z-gnrt))
+	(check-rdct)
+	(setf cat:*tc* (cat:cmbn 1 1 (cat:crpr 1 cat:+null-gbar+ 0 '(1))))
+	(check-rdct)
+	(setf cat:*tc* (cat:cmbn 4 1 (cat:crpr 0 (cat:gbar 4 0 '(10 11 12)
+							   0 '(20 21)
+							   0 '(30) 0 '())
+					       0 '(2 4 6 8))))
+	(check-rdct)
+	(setf cat:*tc* (cat:cmbn 3 1 (cat:crpr 0 (cat:gbar 3 0 '(10 11)
+							   0 '(20) 0 '())
+					       0 '(2 4 6))))
+	(check-rdct)))
+|#
+
+#|
+(test smgr-tnpr-contraction
+      (cat:cat-init)
+      (let* ((chi (cat:smgr-tnpr-contraction (cat:k-z-1)))
+	     (rdct (cat:build-rdct :f (cat:zero-mrph (cat:sorc chi)
+						     (cat:z-chcm))
+				   :g (cat:zero-mrph (cat:z-chcm)
+						     (cat:sorc chi))
+				   :h chi)))
+	(cat:pre-check-rdct rdct)
+	(setf cat:*tc* (cat:cmbn 0 1 (cat:tnpr 0 cat:+null-gbar+ 0 '())))
+	(setf cat:*bc* (cat:cmbn 0 1 :z-gnrt))
+	(check-rdct)
+	(setf cat:*tc* (cat:cmbn 1 1 (cat:tnpr 0 cat:+null-gbar+ 1 '(1))))
+	(check-rdct)
+	(setf cat:*tc* (cat:cmbn 3 1 (cat:tnpr 0 cat:+null-gbar+
+					       3 '(1 10 100))))
+	(cat:? chi cat:*tc*)
+	(check-rdct)
+	(setf cat:*tc* (cat:cmbn 3 1 (cat:tnpr 2 (cat:gbar 2 0 '(1) 0 '())
+					       1 '(10))))
+	(cat:? chi cat:*tc*)
+	(check-rdct)
+	(setf cat:*tc* (cat:cmbn 3 1 (cat:tnpr 3 (cat:gbar 3 0 '(1 10)
+							   0 '(100) 0 '())
+					       0 '())))
+	(cat:? chi cat:*tc*)
+	(check-rdct)
+	(setf cat:*tc* (cat:cmbn 4 1 (cat:tnpr 0 cat:+null-gbar+
+					       4 '(1 10 100 1000))))
+	(cat:? chi cat:*tc*)
+	(check-rdct)
+	(setf cat:*tc* (cat:cmbn 4 1 (cat:tnpr 2 (cat:gbar 2 0 '(1) 0 '())
+					       2 '(10 100))))
+	(cat:? chi cat:*tc*)
+	(check-rdct)
+	(setf cat:*tc* (cat:cmbn 4 1 (cat:tnpr 3 (cat:gbar 3 0 '(1 10)
+							   0 '(100) 0 '())
+				   1 '(1000))))
+	(cat:? chi cat:*tc*)
+	(check-rdct)
+	(setf cat:*tc* (cat:cmbn 4 1 (cat:tnpr 4 (cat:gbar 4 0 '(1 10 100)
+							   0 '(1000 10000)
+							   0 '(100000)
+							   0 '())
+					       0 '())))
+	(cat:? chi cat:*tc*)
+	(check-rdct)))
+|#