diff --git a/LogarithmPlotter/qml/eu/ad5001/LogarithmPlotter/Setting/ExpressionEditor.qml b/LogarithmPlotter/qml/eu/ad5001/LogarithmPlotter/Setting/ExpressionEditor.qml
index 5a758b5..6315e3d 100644
--- a/LogarithmPlotter/qml/eu/ad5001/LogarithmPlotter/Setting/ExpressionEditor.qml
+++ b/LogarithmPlotter/qml/eu/ad5001/LogarithmPlotter/Setting/ExpressionEditor.qml
@@ -433,7 +433,7 @@ Item {
                     itemSelected: parent.itemSelected
                     categoryItems: Parsing.CONSTANTS_LIST
                     autocompleteGenerator: (item) => {return {
-                        'text': item, 'annotation': '',
+                        'text': item, 'annotation': Parsing.CONSTANTS[item],
                         'autocomplete': item + " ", 'cursorFinalOffset': 0
                     }}
                     baseText: parent.visible ? parent.currentToken.value : ""
diff --git a/LogarithmPlotter/qml/eu/ad5001/LogarithmPlotter/js/expr-eval.js b/LogarithmPlotter/qml/eu/ad5001/LogarithmPlotter/js/expr-eval.js
index ae689e8..4bd6ccd 100644
--- a/LogarithmPlotter/qml/eu/ad5001/LogarithmPlotter/js/expr-eval.js
+++ b/LogarithmPlotter/qml/eu/ad5001/LogarithmPlotter/js/expr-eval.js
@@ -27,7 +27,7 @@ var ADDITIONAL_VARCHARS = [
   "ₜ","¹","²","³","⁴","⁵","⁶",
   "⁷","⁸","⁹","⁰","₁","₂","₃",
   "₄","₅","₆","₇","₈","₉","₀",
-  "∞"
+  "∞","π"
 ]
 
 function Instruction(type, value) {
diff --git a/LogarithmPlotter/qml/eu/ad5001/LogarithmPlotter/js/math/common.js b/LogarithmPlotter/qml/eu/ad5001/LogarithmPlotter/js/math/common.js
index 297887b..7eeeb6b 100644
--- a/LogarithmPlotter/qml/eu/ad5001/LogarithmPlotter/js/math/common.js
+++ b/LogarithmPlotter/qml/eu/ad5001/LogarithmPlotter/js/math/common.js
@@ -55,6 +55,8 @@ parser.functions.integral = function(a, b, f, variable) {
 }
 
 parser.functions.derivative = function(f, variable, x) {
+    if(f == null || variable == null || x == null)
+        throw EvalError("Usage: derivative(<function: string>, <variable: string>, <x: number>)")
     f = parser.parse(f).toJSFunction(variable, currentVars)
     return (f(x+DERIVATION_PRECISION/2)-f(x-DERIVATION_PRECISION/2))/DERIVATION_PRECISION
 }
diff --git a/LogarithmPlotter/qml/eu/ad5001/LogarithmPlotter/js/parsing/reference.js b/LogarithmPlotter/qml/eu/ad5001/LogarithmPlotter/js/parsing/reference.js
index ddc3bdd..92baff9 100644
--- a/LogarithmPlotter/qml/eu/ad5001/LogarithmPlotter/js/parsing/reference.js
+++ b/LogarithmPlotter/qml/eu/ad5001/LogarithmPlotter/js/parsing/reference.js
@@ -95,23 +95,5 @@ const FUNCTIONS = {
     'derivative': () => 0,
 }
 const FUNCTIONS_LIST = Object.keys(FUNCTIONS);
-// TODO: Complete
-const DERIVATIVES = {
-    "abs": "abs(<1>)/<1>",
-    "acos": "-derivate(<1>)/sqrt(1-(<1>)^2)",
-    "acosh": "derivate(<1>)/sqrt((<1>)^2-1)",
-    "asin": "derivate(<1>)/sqrt(1-(<1>)^2)",
-    "asinh": "derivate(<1>)/sqrt((<1>)^2+1)",
-    "atan": "derivate(<1>)/(1+(<1>)^2)",
-    "atan2": "",
-}
-const INTEGRALS = {
-    "abs": "integrate(<1>)*sign(<1>)",
-    "acos": "",
-    "acosh": "",
-    "asin": "",
-    "asinh": "",
-    "atan": "",
-    "atan2": "",
-}
+