diff --git a/truth-table.lisp b/truth-table.lisp
index 496b75f..c7f873b 100644
--- a/truth-table.lisp
+++ b/truth-table.lisp
@@ -128,12 +128,14 @@ line."))
   '((open-paren "(")
     (close-paren ")")
     (and "/\\" "and" "&&" "&" "∧" ".")
+    (nand "nand" "↑" "⊼")
     (or "\\/" "or" "||" "|" "∥" "+" "∨")
+    (nor "nor" "↓" "⊽")
     (xor "xor" "⊕" "⊻" "↮" "≢" "^" "!=")
     (not "¬" "~" "!" "not")
     (implies "->" ">" "=>" "⇒" "⟹" "→" "⊃" "implies")
     (converse "<-" "<" "<=" "←" "⇐" "⟸" "⊂" "converse")
-    (iff "<->" "<>" "<=>" "⇔" "↔" "≡" "iff" "=" "=="))
+    (iff "<->" "<>" "<=>" "⇔" "↔" "≡" "iff" "=" "==" "xnor" "⊙"))
   "Alist table of operator symbols and their possible string representations.")
 
 (defun operator-symbol (oper-str)
@@ -147,8 +149,10 @@ line."))
   (case oper
     (not 1)
     (and 2)
+    (nand 2)
     (xor 3)
     (or 4)
+    (nor 4)
     (implies 5)
     (converse 5)
     (iff 6)
@@ -166,6 +170,8 @@ and the maximum number (or nil for infinity) as a second value."
     (implies (values 2 2))
     (converse (values 2 2))
     (iff (values 2 2))
+    (nand (values 2 nil))
+    (nor (values 2 2))
     (t (error "unknown operator: ~S" oper))))
 
 (defun interpret-operand (oper-str)
@@ -398,7 +404,9 @@ found variables."
 
 (defconstant operator-ascii-lookup-alist
   '((and . "&")
+    (nand . "nand")
     (or . "|")
+    (nor . "nor")
     (xor . "^")
     (not . "~")
     (implies . "->")
@@ -412,7 +420,9 @@ found variables."
 
 (defconstant operator-unicode-lookup-alist
   '((and . "∧")
+    (nand . "⊼")
     (or . "∨")
+    (nor . "⊽")
     (xor . "⊕")
     (not . "¬")
     (implies . "→")
@@ -426,7 +436,9 @@ found variables."
 
 (defconstant operator-latex-lookup-alist
   '((and . "\\land")
+    (nand . "\\uparrow")
     (or . "\\lor")
+    (nor . "\\downarrow")
     (xor . "\\oplus")
     (not . "\\lnot ")
     (implies . "\\to")
@@ -589,8 +601,12 @@ NOTE: the second value does not include individual variables, literal values
                         ;; using `eval'
                         (and
                          (apply 'logical-and arg-values))
+                        (nand
+                         (not (apply 'logical-and arg-values)))
                         (or
                          (apply 'logical-or arg-values))
+                        (nor
+                         (not (apply 'logical-or arg-values)))
                         (xor
                          (apply 'logical-xor arg-values))
                         (not