diff --git a/c_src/esqlite3_nif.c b/c_src/esqlite3_nif.c
index 767500c..151d1b7 100644
--- a/c_src/esqlite3_nif.c
+++ b/c_src/esqlite3_nif.c
@@ -1,5 +1,5 @@
 /*
- * Copyright 2011 Maas-Maarten Zeeman
+ * Copyright 2011, 2012 Maas-Maarten Zeeman
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -21,8 +21,6 @@
 #include <erl_nif.h>
 #include <string.h>
 
-#include <stdio.h> /* for debugging */
-
 #include "queue.h"
 #include "sqlite3.h"
 
diff --git a/src/esqlite3.erl b/src/esqlite3.erl
index 83d793d..22c8fa3 100644
--- a/src/esqlite3.erl
+++ b/src/esqlite3.erl
@@ -1,9 +1,9 @@
 %% @author Maas-Maarten Zeeman <mmzeeman@xs4all.nl>
-%% @copyright 2011 Maas-Maarten Zeeman
+%% @copyright 2011, 2012 Maas-Maarten Zeeman
 
 %% @doc Erlang API for sqlite3 databases
 
-%% Copyright 2011 Maas-Maarten Zeeman
+%% Copyright 2011, 2012 Maas-Maarten Zeeman
 %%
 %% Licensed under the Apache License, Version 2.0 (the "License");
 %% you may not use this file except in compliance with the License.
@@ -33,17 +33,24 @@
 
 -export([q/2, q/3, map/3, foreach/3]).
 
--define(DEFAULT_TIMEOUT, infinity).
+-define(DEFAULT_TIMEOUT, 5000).
+
+%% 
+-type connection() :: tuple().
+-type statement() :: term().
+-type sql() :: iolist().
 
 %% @doc Opens a sqlite3 database mentioned in Filename.
 %%
-%% @spec open(string()) -> {ok, connection()} | {error, error_message()}
+-spec open(FileName) -> {ok, connection()} | {error, _} when
+    FileName :: string().
 open(Filename) ->
     open(Filename, ?DEFAULT_TIMEOUT).
 
 %% @doc Open a database connection
 %%
-%% @spec open(string(), timeout()) -> {ok, connection()} | {error, error_message()}
+-spec open(Filename, timeout()) -> {ok, connection()} | {error, _} when
+    Filename :: string().
 open(Filename, Timeout) ->
     {ok, Connection} = esqlite3_nif:start(),
 
@@ -51,51 +58,66 @@ open(Filename, Timeout) ->
     ok = esqlite3_nif:open(Connection, Ref, self(), Filename),
     case receive_answer(Ref, Timeout) of
         ok ->
-            {ok, Connection};
+            {ok, {connection, make_ref(), Connection}};
         {error, _Msg}=Error ->
             Error
     end.
 
-%% @doc Execute a sql statement, returns a list with tuples. 
+%% @doc Execute a sql statement, returns a list with tuples.
+-spec q(sql(), connection()) -> list(tuple()).
 q(Sql, Connection) ->
     q(Sql, [], Connection).
 
 %% @doc Execute statement, bind args and return a list with tuples as result.
+-spec q(sql(), list(), connection()) -> list(tuple()).
 q(Sql, [], Connection) ->
     case prepare(Sql, Connection) of
         {ok, Statement} -> 
             fetchall(Statement);
-        {error, _Msg}=E -> 
-            throw(E)
+        {error, _Msg}=Error -> 
+            throw(Error)
     end;
 q(Sql, Args, Connection) ->
     case prepare(Sql, Connection) of
         {ok, Statement} ->
             ok = bind(Statement, Args),
             fetchall(Statement);
-        {error, _Msg}=E -> 
-            throw(E)
+        {error, _Msg}=Error -> 
+            throw(Error)
     end.
 
-%% 
+%% @doc
+-spec map(F, sql(), connection()) -> list(Type) when
+    F :: fun((Row) -> Type) | fun((ColumnNames, Row) -> Type),
+    Row :: tuple(),
+    ColumnNames :: tuple(),
+    Type :: any(). 
 map(F, Sql, Connection) ->
     case prepare(Sql, Connection) of
         {ok, Statement} ->
             map_s(F, Statement);
-        {error, _Msg}=E -> 
-            throw(E)
+        {error, _Msg}=Error -> 
+            throw(Error)
     end.
 
-%% 
+%% @doc
+-spec foreach(F, sql(), connection()) -> ok when
+    F :: fun((Row) -> any()) | fun((ColumnNames, Row) -> any()),
+    Row :: tuple(),
+    ColumnNames :: tuple().
 foreach(F, Sql, Connection) ->
     case prepare(Sql, Connection) of
         {ok, Statement} ->
             foreach_s(F, Statement);
-        {error, _Msg}=E ->
-            throw(E)
+        {error, _Msg}=Error ->
+            throw(Error)
     end.
 
 %%
+-spec foreach_s(F, statement()) -> ok when
+    F :: fun((Row) -> any()) | fun((ColumnNames, Row) -> any()),
+    Row :: tuple(),
+    ColumnNames :: tuple().
 foreach_s(F, Statement) when is_function(F, 1) -> 
     case try_step(Statement, 0) of
         '$done' -> ok;
@@ -113,6 +135,11 @@ foreach_s(F, Statement) when is_function(F, 2) ->
     end.
 
 %%
+-spec map_s(F, statement()) -> list(Type) when
+    F :: fun((Row) -> Type) | fun((ColumnNames, Row) -> Type),
+    Row :: tuple(),
+    ColumnNames :: tuple(),
+    Type :: term().
 map_s(F, Statement) when is_function(F, 1) ->
     case try_step(Statement, 0) of
         '$done' -> [];
@@ -128,13 +155,15 @@ map_s(F, Statement) when is_function(F, 2) ->
     end.
 
 %%
+-spec fetchone(statement()) -> tuple().
 fetchone(Statement) ->
     case try_step(Statement, 0) of
         '$done' -> ok;
         {row, Row} -> Row
     end.
 
-%%    
+%% 
+-spec fetchall(statement()) -> list(tuple()).
 fetchall(Statement) ->
     case try_step(Statement, 0) of
         '$done' -> 
@@ -144,6 +173,7 @@ fetchall(Statement) ->
     end.  
 
 %% Try the step, when the database is busy, 
+-spec try_step(statement(), non_neg_integer()) -> term().
 try_step(_Statement, Tries) when Tries > 5 ->
     throw(too_many_tries);
 try_step(Statement, Tries) ->
@@ -164,7 +194,7 @@ exec(Sql, Connection) ->
 %% @doc Execute 
 %%
 %% @spec exec(iolist(), connection(), timeout()) -> integer() | {error, error_message()}
-exec(Sql, Connection, Timeout) ->
+exec(Sql, {connection, _Ref, Connection}, Timeout) ->
     Ref = make_ref(),
     ok = esqlite3_nif:exec(Connection, Ref, self(), add_eos(Sql)),
     receive_answer(Ref, Timeout).
@@ -178,7 +208,7 @@ prepare(Sql, Connection) ->
 %% @doc
 %%
 %% @spec(iolist(), connection(), timeout()) -> {ok, prepared_statement()} | {error, error_message()}
-prepare(Sql, Connection, Timeout) ->
+prepare(Sql, {connection, _Ref, Connection}, Timeout) ->
     Ref = make_ref(),
     ok = esqlite3_nif:prepare(Connection, Ref, self(), add_eos(Sql)),
     receive_answer(Ref, Timeout).
@@ -224,13 +254,15 @@ column_names(Stmt, Timeout) ->
 %% @doc Close the database
 %%
 %% @spec close(connection()) -> ok | {error, error_message()}
+-spec close(connection()) -> ok | {error, _}.
 close(Connection) ->
     close(Connection, ?DEFAULT_TIMEOUT).
 
 %% @doc Close the database
 %%
 %% @spec close(connection(), integer()) -> ok | {error, error_message()}
-close(Connection, Timeout) ->
+-spec close(connection(), timeout()) -> ok | {error, _}.
+close({connection, _Ref, Connection}, Timeout) ->
     Ref = make_ref(),
     ok = esqlite3_nif:close(Connection, Ref, self()),
     receive_answer(Ref, Timeout).
@@ -246,8 +278,3 @@ receive_answer(Ref, Timeout) ->
     after Timeout ->
         throw({error, timeout, Ref})
     end.
-
-    
-
-
-
diff --git a/src/esqlite3_nif.erl b/src/esqlite3_nif.erl
index 3f1c37b..794a326 100644
--- a/src/esqlite3_nif.erl
+++ b/src/esqlite3_nif.erl
@@ -1,9 +1,9 @@
 %% @author Maas-Maarten Zeeman <mmzeeman@xs4all.nl>
-%% @copyright 2011 Maas-Maarten Zeeman
+%% @copyright 2011, 2012 Maas-Maarten Zeeman
 
 %% @doc Low level erlang API for sqlite3 databases
 
-%% Copyright 2011 Maas-Maarten Zeeman
+%% Copyright 2011, 2012 Maas-Maarten Zeeman
 %%
 %% Licensed under the Apache License, Version 2.0 (the "License");
 %% you may not use this file except in compliance with the License.