diff --git a/src/client/mod.rs b/src/client/mod.rs
index c3b740b..bd09e64 100644
--- a/src/client/mod.rs
+++ b/src/client/mod.rs
@@ -160,7 +160,7 @@ impl<S: Connecter + ClientStream + Clone> Client<S> {
     /// * If `message` is `None`, the given command will be formatted and sent to the server
     /// * If `message` is `Some(str)`, the `str` string will be sent to the server
     fn send_server(&mut self, command: Command, message: Option<&str>) -> SmtpResult {
-        if !self.state.is_command_possible(command.clone()) {
+        if !self.state.is_command_allowed(command.clone()) {
             fail_with_err!(Response{code: 503, message: Some("Bad sequence of commands".to_string())} self);
         }
 
diff --git a/src/client/stream.rs b/src/client/stream.rs
index dbdc686..17dac5f 100644
--- a/src/client/stream.rs
+++ b/src/client/stream.rs
@@ -32,7 +32,7 @@ pub trait ClientStream {
 }
 
 impl ClientStream for TcpStream {
-    /// Sends a string to the server and get the response
+    /// Sends a string to the server and gets the response
     fn send_and_get_response(&mut self, string: &str, end: &str) -> SmtpResult {
         try!(self.write_str(format!("{}{}", escape_dot(string), end).as_slice()));
 
diff --git a/src/command.rs b/src/command.rs
index cb82a90..d8b7e27 100644
--- a/src/command.rs
+++ b/src/command.rs
@@ -33,9 +33,9 @@ pub enum Command {
     ExtendedHello(String),
     /// Hello command
     Hello(String),
-    /// Mail command, takes optionnal options
+    /// Mail command, takes optional options
     Mail(String, Option<Vec<String>>),
-    /// Recipient command, takes optionnal options
+    /// Recipient command, takes optional options
     Recipient(String, Option<Vec<String>>),
     /// Data command
     Data,
@@ -43,11 +43,11 @@ pub enum Command {
     Message,
     /// Reset command
     Reset,
-    /// Verify command, takes optionnal options
+    /// Verify command, takes optional options
     Verify(String),
-    /// Expand command, takes optionnal options
+    /// Expand command, takes optional options
     Expand(String),
-    /// Help command, takes optionnal options
+    /// Help command, takes optional options
     Help(Option<String>),
     /// Noop command
     Noop,
diff --git a/src/response.rs b/src/response.rs
index 1a46fb7..6a8f9dc 100644
--- a/src/response.rs
+++ b/src/response.rs
@@ -18,12 +18,12 @@ use common::remove_trailing_crlf;
 
 /// Contains an SMTP reply, with separed code and message
 ///
-/// We do accept messages containing only a code, to comply with RFC5321
+/// The text message is optional, only the code is mandatory
 #[deriving(PartialEq,Eq,Clone)]
 pub struct Response {
     /// Server response code
     pub code: u16,
-    /// Server response string (optionnal)
+    /// Server response string (optional)
     pub message: Option<String>
 }
 
diff --git a/src/transaction.rs b/src/transaction.rs
index 252ba62..592b161 100644
--- a/src/transaction.rs
+++ b/src/transaction.rs
@@ -54,8 +54,9 @@ impl TransactionState {
     pub fn new() -> TransactionState {
         Unconnected
     }
-    /// TODO
-    pub fn is_command_possible(&self, command: Command) -> bool {
+
+    /// Tests if the given command is allowed in the current state
+    pub fn is_command_allowed(&self, command: Command) -> bool {
         match (*self, command) {
             (Unconnected, command::Connect) => true,
             (Unconnected, _) => false,
@@ -81,7 +82,9 @@ impl TransactionState {
         }
     }
 
-    /// TODO
+    /// Returns the state resulting of the given command
+    ///
+    /// A `None` return value means the comand is not allowed.
     pub fn next_state(&mut self, command: Command) -> Option<TransactionState> {
         match (*self, command) {
             (Unconnected, command::Connect) => Some(Connected),
@@ -120,11 +123,11 @@ mod test {
     }
 
     #[test]
-    fn test_is_command_possible() {
-        assert!(!super::Unconnected.is_command_possible(command::Noop));
-        assert!(!super::DataSent.is_command_possible(command::Noop));
-        assert!(super::HelloSent.is_command_possible(command::Mail("".to_string(), None)));
-        assert!(!super::MailSent.is_command_possible(command::Mail("".to_string(), None)));
+    fn test_is_command_allowed() {
+        assert!(!super::Unconnected.is_command_allowed(command::Noop));
+        assert!(!super::DataSent.is_command_allowed(command::Noop));
+        assert!(super::HelloSent.is_command_allowed(command::Mail("".to_string(), None)));
+        assert!(!super::MailSent.is_command_allowed(command::Mail("".to_string(), None)));
     }
 
     #[test]