+(* equality, conguence ******************************************************)
+
+notation > "hvbox(a break = b)"
+ non associative with precedence 45
+for @{ 'eq ? $a $b }.
+
+notation < "hvbox(term 46 a break maction (=) (=\sub t) term 46 b)"
+ non associative with precedence 45
+for @{ 'eq $t $a $b }.
+
+notation > "hvbox(n break (≅ \sub term 90 p) m)"
+ non associative with precedence 45
+for @{ 'congruent $n $m $p }.
+
+notation < "hvbox(term 46 n break ≅ \sub p term 46 m)"
+ non associative with precedence 45
+for @{ 'congruent $n $m $p }.
+
+(* other notations **********************************************************)
+