diff --git a/Cargo.toml b/Cargo.toml
index b85ae18..468aa45 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -7,5 +7,6 @@ edition = "2024"
 lalrpop = "0.22"
 
 [dependencies]
+petgraph = { version = "0.8" }
 regex = { version = "1.11", features = ["unicode-bool"] }
 lalrpop-util = { version = "0.22", features = ["lexer", "unicode"] }
diff --git a/src/main.rs b/src/main.rs
index cd2a8a0..56c36c3 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -11,9 +11,9 @@ fn main() -> std::io::Result<()> {
     // std::thread::sleep(std::time::Duration::new(2, 0));
     // println!("{}", now.elapsed().as_micros());
 
-    examples::stats()?;
+    // examples::stats()?;
 
-    // examples::freq()?;
+    examples::freq()?;
 
     // examples::hoop()?;
 
@@ -23,7 +23,7 @@ fn main() -> std::io::Result<()> {
 
     // examples::limit_freq()?;
 
-    examples::fast_freq()?;
+    // examples::fast_freq()?;
 
     Ok(())
 }
diff --git a/src/rsprocess/grammar.lalrpop b/src/rsprocess/grammar.lalrpop
index 6c7eeba..bbc8673 100644
--- a/src/rsprocess/grammar.lalrpop
+++ b/src/rsprocess/grammar.lalrpop
@@ -19,6 +19,16 @@ grammar(translator: &mut Translator);
 
 // order
 match {
+    "nill",
+    "{", "}",
+    "[", "]",
+    "(", ")",
+    "<", ">",
+    "r:", "i:", "p:",
+    "-", "^",
+    "true", "false",
+    "inW", "inR", "inI", "inP"
+} else {
     r"[0-9]+" => NUMBER
 } else {
     // r"([[:alpha:]]|\p{Emoji})([[:word:]]|\p{Emoji})*" => WORD
@@ -98,6 +108,7 @@ Boxed_CTX_process: Rc<RSprocess> = {
 }
 
 CTX_process: RSprocess = {
+    "nill" => RSprocess::Nill,
     <c: Set_of_entities> "." <k: CTX_process> =>
 	RSprocess::EntitySet{ entities: c, next_process: Rc::new(k) },
     "(" <k: CTX_process>  ")" => k,
@@ -109,7 +120,6 @@ CTX_process: RSprocess = {
 	RSprocess::WaitEntity{ repeat: n,
 			       repeated_process: Rc::new(k1),
 			       next_process: Rc::new(k) },
-    "nill" => RSprocess::Nill,
     <identifier: Literal> =>
 	RSprocess::RecursiveIdentifier{
 		identifier: translator.encode(identifier)
diff --git a/src/rsprocess/transitions.rs b/src/rsprocess/transitions.rs
index 6bc7378..ec3d9d2 100644
--- a/src/rsprocess/transitions.rs
+++ b/src/rsprocess/transitions.rs
@@ -21,7 +21,7 @@ pub fn unfold(
             if let Some(newprocess) = newprocess {
                 unfold(environment, newprocess)
             } else {
-                Err(format!("Recursive call to missing symbol: {identifier}"))
+                Err(format!("Missing symbol in context: {identifier}"))
             }
         }
         RSprocess::EntitySet {
diff --git a/testing/first.experiment b/testing/first.experiment
index 0b289d6..9a30e62 100644
--- a/testing/first.experiment
+++ b/testing/first.experiment
@@ -1,2 +1,2 @@
 Weights: 10,10
-Sets: {a,b},{a, 㐀, 豈}
\ No newline at end of file
+Sets: {a,b},{a}
\ No newline at end of file
diff --git a/testing/first.system b/testing/first.system
index 8d16057..3314710 100644
--- a/testing/first.system
+++ b/testing/first.system
@@ -1,4 +1,4 @@
-Environment: [x = {a}.ñ, ñ =({a}.nill + {b}.nill)]
+Environment: [x = {a}.y, y =({a}.nill + {b}.nill)]
 Initial Entities: {a, b}
-Context: [({a,b}.{a}.{a,c}.x + {a,b}.{a}.{a}.nil)]
-Reactions: ([r: {a,b}, i: {c}, p: {b, ñ, 㐀, 豈, a12-3, 🙏}])
+Context: [({a,b}.{a}.{a,c}.x + {a,b}.{a}.{a}.nill)]
+Reactions: ([r: {a,b}, i: {c}, p: {b}])