diff --git a/ontologies/periods/atomic_periods.clif b/ontologies/periods/atomic_periods.clif
index dd2e94af4..cac2dd268 100644
--- a/ontologies/periods/atomic_periods.clif
+++ b/ontologies/periods/atomic_periods.clif
@@ -2,7 +2,7 @@
 
 (cl-imports http://colore.oor.net/periods/finite_periods.clif)
 
-(cl-comment "ATOM")
+(cl-comment 'ATOM')
 (forall	(x)
 	(exists (y)
 		(and	(inclusion y x)
diff --git a/ontologies/periods/cem_periods.clif b/ontologies/periods/cem_periods.clif
index 84a1e79f7..13c4a6813 100644
--- a/ontologies/periods/cem_periods.clif
+++ b/ontologies/periods/cem_periods.clif
@@ -5,20 +5,20 @@
 
 (cl-imports http://colore.oor.net/periods/definitions/periods_def.clif)
 
-(cl-comment "DISJ")
+(cl-comment 'DISJ')
 (forall (x y)
         (if     (underlaps x y)
                 (exists (z)
                         (lub x y z))))
 
-(cl-comment "FREE")
+(cl-comment 'FREE')
 (forall (x y)
 (if             (not    (inclusion x y))
                 (exists (z)
                                 (and    (inclusion z x)
                                                 (not    (overlaps z y))))))
 
-(cl-comment "CONJ")
+(cl-comment 'CONJ')
 (forall (x y)
 	(if	(overlaps x y)
 		(exists (z)
diff --git a/ontologies/periods/definitions/periods_def.clif b/ontologies/periods/definitions/periods_def.clif
index 02734d873..3bc8bd3b2 100644
--- a/ontologies/periods/definitions/periods_def.clif
+++ b/ontologies/periods/definitions/periods_def.clif
@@ -2,14 +2,14 @@
 
 (cl-imports http://colore.oor.net/periods/periods_root.clif)
 
-(cl-comment "Overlaps")
+(cl-comment 'Overlaps')
 (forall	(x y)
 (iff	(overlaps x y)
 	(exists	(z)
 		(and	(inclusion z x)
 			(inclusion z y)))))
 
-(cl-comment "Greatest Lower Bound")
+(cl-comment 'Greatest Lower Bound')
 (forall (x y z)
 (iff	(glb x y z)
 	(and	(inclusion z x)
@@ -19,14 +19,14 @@
 					(inclusion u y))
 				(inclusion u z))))))
 
-(cl-comment "Underlaps")
+(cl-comment 'Underlaps')
 (forall (x y)
 (iff    (underlaps x y)
 	(exists (z)
 		(and    (inclusion x z)
 			(inclusion y z)))))
 
-(cl-comment "Lower Upper Bound")
+(cl-comment 'Lower Upper Bound')
 (forall (x y z)
 (iff    (lub x y z)
 	(and    (inclusion x z)
diff --git a/ontologies/periods/directed_periods.clif b/ontologies/periods/directed_periods.clif
index 92272b053..c0783a143 100644
--- a/ontologies/periods/directed_periods.clif
+++ b/ontologies/periods/directed_periods.clif
@@ -3,7 +3,7 @@
 
 (cl-imports http://colore.oor.net/periods/periods.clif)
 
-(cl-comment "DIR")
+(cl-comment 'DIR')
 (forall (x y)
                 (exists (z)
                                 (and    (inclusion x z)
diff --git a/ontologies/periods/finite_periods.clif b/ontologies/periods/finite_periods.clif
index a18f42cf4..fc067a02d 100644
--- a/ontologies/periods/finite_periods.clif
+++ b/ontologies/periods/finite_periods.clif
@@ -7,20 +7,20 @@
 
 (cl-imports http://colore.oor.net/periods/definitions/periods_def.clif)
 
-(cl-comment "DISJ")
+(cl-comment 'DISJ')
 (forall (x y)
         (if     (underlaps x y)
                 (exists (z)
                         (lub x y z))))
 
-(cl-comment "FREE")
+(cl-comment 'FREE')
 (forall (x y)
 (if             (not    (inclusion x y))
                 (exists (z)
                                 (and    (inclusion z x)
                                                 (not    (overlaps z y))))))
 
-(cl-comment "MOND-1")
+(cl-comment 'MOND-1')
 (forall (x y z)
 (if             (and    (precedence x y)
                         (precedence z y))
@@ -28,7 +28,7 @@
                                 (and    (lub x z w)
                                         (precedence w y)))))
 
-(cl-comment "MOND-2")
+(cl-comment 'MOND-2')
 (forall (x y z)
 (if             (and    (precedence y x)
 			(precedence y z))
@@ -36,7 +36,7 @@
                                 (and    (lub x z w)
                                         (precedence y w)))))
 
-(cl-comment "CONV")
+(cl-comment 'CONV')
 (forall (x y z)
 (if             (and    (precedence x y)
                                 (precedence y z))
diff --git a/ontologies/periods/infinite_periods.clif b/ontologies/periods/infinite_periods.clif
index 1b4b6cf94..9aa84c558 100644
--- a/ontologies/periods/infinite_periods.clif
+++ b/ontologies/periods/infinite_periods.clif
@@ -3,12 +3,12 @@
 
 (cl-imports http://colore.oor.net/periods/periods.clif)
 
-(cl-comment "SUCC-1")
+(cl-comment 'SUCC-1')
 (forall (x)
                 (exists (y)
                                 (precedence x y)))
 
-(cl-comment "SUCC-2")
+(cl-comment 'SUCC-2')
 (forall (x)
                 (exists (y)
                                 (precedence y x)))
diff --git a/ontologies/periods/linear_periods.clif b/ontologies/periods/linear_periods.clif
index 0a8766f43..0adba0a02 100644
--- a/ontologies/periods/linear_periods.clif
+++ b/ontologies/periods/linear_periods.clif
@@ -5,7 +5,7 @@
 
 (cl-imports http://colore.oor.net/periods/definitions/periods_def.clif)
 
-(cl-comment "LIN*")
+(cl-comment 'LIN*')
 (forall (x y)
 (or             (precedence x y)
                 (precedence y x)
diff --git a/ontologies/periods/mixed_periods.clif b/ontologies/periods/mixed_periods.clif
index f10830201..e81045a77 100644
--- a/ontologies/periods/mixed_periods.clif
+++ b/ontologies/periods/mixed_periods.clif
@@ -6,7 +6,7 @@
 
 (cl-imports http://colore.oor.net/periods/definitions/periods_def.clif)
 
-(cl-comment "NEIGH-1")
+(cl-comment 'NEIGH-1')
 (forall (x y)
 (if		(precedence x y)
 		(exists (w)
@@ -15,7 +15,7 @@
 										(and	(precedence x z)
 												(precedence z w))))))))
 
-(cl-comment "NEIGH-2")
+(cl-comment 'NEIGH-2')
 (forall (x y)
 	(if	(precedence y x)
 		(exists (w)
diff --git a/ontologies/periods/periods.clif b/ontologies/periods/periods.clif
index 7389f64bd..ada84a27e 100644
--- a/ontologies/periods/periods.clif
+++ b/ontologies/periods/periods.clif
@@ -4,13 +4,13 @@
 
 (cl-imports http://colore.oor.net/periods/definitions/periods_def.clif)
 
-(cl-comment "MON-2")
+(cl-comment 'MON-2')
 (forall (x y z)
 (if     (and    (precedence x y)
 		(inclusion z y))
         (precedence x z)))
 
-(cl-comment "CONJ")
+(cl-comment 'CONJ')
 (forall	(x y)
 (if	(overlaps x y)
 	(exists	(z)
diff --git a/ontologies/periods/periods_over_rationals.clif b/ontologies/periods/periods_over_rationals.clif
index 7537808ab..81405708e 100644
--- a/ontologies/periods/periods_over_rationals.clif
+++ b/ontologies/periods/periods_over_rationals.clif
@@ -2,13 +2,13 @@
 
 (cl-imports http://colore.oor.net/periods/mixed_periods.clif)
 
-(cl-comment "DENS*")
+(cl-comment 'DENS*')
 (forall	(x)
 		(exists	(y1 y2)
 				(and	(precedence y1 y2)
 						(lub y1 y2 x))))
 
-(cl-comment "ORIENT")
+(cl-comment 'ORIENT')
 (forall	(x y)
 (if		(overlaps x y)
 		(or		(= x y)
diff --git a/ontologies/periods/periods_root.clif b/ontologies/periods/periods_root.clif
index dbea934d3..0a73d9e50 100644
--- a/ontologies/periods/periods_root.clif
+++ b/ontologies/periods/periods_root.clif
@@ -1,32 +1,32 @@
 (cl-text http://colore.oor.net/periods/periods_root.clif
 
-(cl-comment "Precedence TRANS")
+(cl-comment 'Precedence TRANS')
 (forall	(x y z) 
 (if	(and	(precedence x y)
 		(precedence y z))
 	(precedence x z)))
 
-(cl-comment "Precedence IREFF")
+(cl-comment 'Precedence IREFF')
 (forall	(x)
 	(not	(precedence x x)))
 
-(cl-comment "Inclusion TRANS")
+(cl-comment 'Inclusion TRANS')
 (forall	(x y z) 
 (if	(and	(inclusion x y)
 		(inclusion y z))
 	(inclusion x z)))
 
-(cl-comment "Inclusion REF")
+(cl-comment 'Inclusion REF')
 (forall	(x)
 	(inclusion x x))
 
-(cl-comment "Inclusion ANTIS")
+(cl-comment 'Inclusion ANTIS')
 (forall	(x y)
 (if	(and	(inclusion x y)
 		(inclusion y x))
 	(= x y)))
 
-(cl-comment "MON-1")
+(cl-comment 'MON-1')
 (forall (x y z)
 (if	(and	(precedence x y)
 		(inclusion z x))