diff --git a/index.d.ts b/index.d.ts
index ee9a43a..9040300 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -1,50 +1,130 @@
-import { Unsubscribe } from 'redux';
+import { Action, AnyAction, Unsubscribe } from 'redux';
 
 declare namespace ngRedux {
-  export interface Reducer extends Function {
-      (state: any, action: any): any;
-  }
 
-  export interface Dispatch extends Function {
-      (action: any): any;
+  export type Reducer<S = any, A extends Action = AnyAction> = (state: S | undefined, action: A) => S;
+
+  export interface Dispatch<A extends Action = AnyAction> {
+    <T extends A>(action: T): T;
   }
 
-  export interface MiddlewareArg {
-      dispatch: Dispatch;
-      getState: Function;
+  export interface MiddlewareArg<D extends Dispatch = Dispatch, S = any> {
+    dispatch: D;
+    getState(): S;
   }
 
-  export interface Middleware extends Function {
-      (obj: MiddlewareArg): Function;
+  export interface Middleware<DispatchExt = {}, S = any, D extends Dispatch = Dispatch> {
+    (api: MiddlewareArg<D, S>): (next: Dispatch<AnyAction>) => (action: any) => any;
   }
 
+  /* config */
+
   export interface Config {
-      debounce: DebounceConfig;
+    debounce: DebounceConfig;
   }
-  
+
   export interface DebounceConfig {
-      wait?: number;
-      maxWait?: number;
+    wait?: number;
+    maxWait?: number;
   }
 
+  /* API */
+
   export interface INgRedux {
-      getReducer(): Reducer;
-      replaceReducer(nextReducer: Reducer): void;
-      dispatch(action: any): any;
-      getState(): any;
-      subscribe(listener: Function): Unsubscribe;
-      connect(
-          mapStateToTarget: (state: any) => Object,
-          mapDispatchToTarget?: Object | ((dispatch: Function) => Object)
-      ): (target: Function | Object) => () => void;
+    /**
+     * Replaces the reducer currently used by the store to calculate the state.
+     *
+     * You might need this if your app implements code splitting and you want to
+     * load some of the reducers dynamically. You might also need this if you
+     * implement a hot reloading mechanism for Redux.
+     *
+     * @param nextReducer The reducer for the store to use instead.
+     */
+    replaceReducer(nextReducer: Reducer): void;
+    /**
+     * A *dispatching function* (or simply *dispatch function*) is a function that
+     * accepts an action or an async action; it then may or may not dispatch one
+     * or more actions to the store.
+     *
+     * We must distinguish between dispatching functions in general and the base
+     * `dispatch` function provided by the store instance without any middleware.
+     *
+     * The base dispatch function *always* synchronously sends an action to the
+     * store's reducer, along with the previous state returned by the store, to
+     * calculate a new state. It expects actions to be plain objects ready to be
+     * consumed by the reducer.
+     *
+     * Middleware wraps the base dispatch function. It allows the dispatch
+     * function to handle async actions in addition to actions. Middleware may
+     * transform, delay, ignore, or otherwise interpret actions or async actions
+     * before passing them to the next middleware.
+     *
+     * @template A The type of things (actions or otherwise) which may be
+     *   dispatched.
+     */
+    dispatch<A extends Action>(action: A): A;
+    /**
+     * Reads the state tree managed by the store.
+     *
+     * @returns The current state tree of your application.
+     */
+    getState<S = any>(): S;
+    /**
+     * Adds a change listener. It will be called any time an action is
+     * dispatched, and some part of the state tree may potentially have changed.
+     * You may then call `getState()` to read the current state tree inside the
+     * callback.
+     *
+     * You may call `dispatch()` from a change listener, with the following
+     * caveats:
+     *
+     * 1. The subscriptions are snapshotted just before every `dispatch()` call.
+     * If you subscribe or unsubscribe while the listeners are being invoked,
+     * this will not have any effect on the `dispatch()` that is currently in
+     * progress. However, the next `dispatch()` call, whether nested or not,
+     * will use a more recent snapshot of the subscription list.
+     *
+     * 2. The listener should not expect to see all states changes, as the state
+     * might have been updated multiple times during a nested `dispatch()` before
+     * the listener is called. It is, however, guaranteed that all subscribers
+     * registered before the `dispatch()` started will be called with the latest
+     * state by the time it exits.
+     *
+     * @param listener A callback to be invoked on every dispatch.
+     * @returns A function to remove this change listener.
+     */
+    subscribe(listener: () => void): Unsubscribe;
+    /**
+     * Connects a component to a Redux store.
+     *
+     * @param mapStateToTarget
+     * @param mapDispatchToTarget
+     */
+    connect(
+      mapStateToTarget: null | ((state: any) => { [key: string]: any; }),
+      mapDispatchToTarget?: object | ((dispatch: Function) => object)
+    ): (target: Function | object) => Unsubscribe;
   }
 
+  /* provider */
+
   export interface INgReduxProvider {
-      createStoreWith(reducer: Reducer, middlewares?: Array<Middleware | string>, storeEnhancers?: Function[], initialState?: any): void;
-      config: Config;
+    /**
+     * Creates Redux store.
+     *
+     * @param reducer
+     * @param middlewares
+     * @param storeEnhancers
+     * @param initialState
+     */
+    createStoreWith<S = any, I = any>(reducer: Reducer<S>, middlewares?: (Middleware | string)[], storeEnhancers?: Function[], initialState?: I): void;
+    /**
+     * ngRedux config object
+     */
+    config: Config;
   }
 }
 
 declare var ngRedux: string;
 export as namespace ngRedux;
-export default ngRedux;
+export default ngRedux;
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