diff --git a/store/configureStore.development.ts b/store/configureStore.development.ts
index c28a81d..2b4fce9 100644
--- a/store/configureStore.development.ts
+++ b/store/configureStore.development.ts
@@ -1,13 +1,12 @@
 import { applyMiddleware, createStore } from "redux"
 import { composeWithDevTools } from "redux-devtools-extension"
 import createSagaMiddleware from "redux-saga"
-import { combinedReducers } from "./reducers"
+import { combinedReducers, RootState } from "./reducers"
 import { rootSaga } from "./sagas"
-import { IInitialState } from "./states"
 
 const sagaMiddleware = createSagaMiddleware()
 
-export function configureStore(initialState?: IInitialState) {
+export function configureStore(initialState?: RootState) {
   const store = createStore(
     combinedReducers,
     initialState,
diff --git a/store/configureStore.production.ts b/store/configureStore.production.ts
index 6add60f..7f16422 100644
--- a/store/configureStore.production.ts
+++ b/store/configureStore.production.ts
@@ -1,12 +1,11 @@
 import { applyMiddleware, createStore } from "redux"
 import createSagaMiddleware from "redux-saga"
-import { combinedReducers } from "./reducers"
+import { combinedReducers, RootState } from "./reducers"
 import { rootSaga } from "./sagas"
-import { IInitialState } from "./states"
 
 const sagaMiddleware = createSagaMiddleware()
 
-export function configureStore(initialState?: IInitialState) {
+export function configureStore(initialState?: RootState) {
   const store = createStore(
     combinedReducers,
     initialState,
diff --git a/store/configureStore.ts b/store/configureStore.ts
index 0d460fc..3cceb31 100644
--- a/store/configureStore.ts
+++ b/store/configureStore.ts
@@ -1,5 +1,5 @@
 import { Env } from "../constants"
-import { IInitialState } from "../store/states"
+import { RootState } from "./reducers"
 
 const configureStoreComponent = (() => {
   if (Env.NODE_ENV === "production") {
@@ -8,5 +8,5 @@ const configureStoreComponent = (() => {
   return require("./configureStore.development")
 })()
 
-export const configureStore = (initialState?: IInitialState) =>
+export const configureStore = (initialState?: RootState) =>
   configureStoreComponent.configureStore(initialState)
diff --git a/store/counter/selectors.ts b/store/counter/selectors.ts
index f10059e..d82e040 100644
--- a/store/counter/selectors.ts
+++ b/store/counter/selectors.ts
@@ -1,3 +1,3 @@
-import { IInitialState } from "../states"
+import { RootState } from "../reducers"
 
-export const countSelector = (state: IInitialState) => state.counter.count
+export const countSelector = (state: RootState) => state.counter.count
diff --git a/store/page/selectors.ts b/store/page/selectors.ts
index 4e1bf39..e45c2b8 100644
--- a/store/page/selectors.ts
+++ b/store/page/selectors.ts
@@ -1,4 +1,4 @@
-import { IInitialState } from "../states"
+import { RootState } from "../reducers"
 
-export const selectedPageSelector = (state: IInitialState) =>
+export const selectedPageSelector = (state: RootState) =>
   state.page.selectedPage
diff --git a/store/reducers.ts b/store/reducers.ts
index 821c2e3..641125a 100644
--- a/store/reducers.ts
+++ b/store/reducers.ts
@@ -5,11 +5,12 @@ import {
   reduxSagaDebounceReducer,
   reduxSagaThrottleReducer,
 } from "./redux-saga/reducers"
-import { IInitialState } from "./states"
 
-export const combinedReducers = combineReducers<IInitialState>({
+export const combinedReducers = combineReducers({
   counter: countReducer,
   page: pageReducer,
   reduxSagaDebounce: reduxSagaDebounceReducer,
   reduxSagaThrottle: reduxSagaThrottleReducer,
 })
+
+export type RootState = ReturnType<typeof combinedReducers>
diff --git a/store/redux-saga/selectors.ts b/store/redux-saga/selectors.ts
index 87118d0..326bb23 100644
--- a/store/redux-saga/selectors.ts
+++ b/store/redux-saga/selectors.ts
@@ -1,10 +1,8 @@
-import { IInitialState } from "../states"
+import { RootState } from "../reducers"
 import { IReduxSagaState } from "./states"
 
-export const reduxSagaDebounceSelector = (
-  state: IInitialState
-): IReduxSagaState => state.reduxSagaDebounce
+export const reduxSagaDebounceSelector = (state: RootState): IReduxSagaState =>
+  state.reduxSagaDebounce
 
-export const reduxSagaThrottleSelector = (
-  state: IInitialState
-): IReduxSagaState => state.reduxSagaThrottle
+export const reduxSagaThrottleSelector = (state: RootState): IReduxSagaState =>
+  state.reduxSagaThrottle
diff --git a/store/states.ts b/store/states.ts
deleted file mode 100644
index 8decd04..0000000
--- a/store/states.ts
+++ /dev/null
@@ -1,13 +0,0 @@
-import { ICounterState } from "./counter"
-import { IPageState } from "./page"
-import { IReduxSagaState } from "./redux-saga"
-
-/**
- * Initial state tree interface
- */
-export interface IInitialState {
-  counter: Readonly<ICounterState>
-  page: Readonly<IPageState>
-  reduxSagaDebounce: Readonly<IReduxSagaState>
-  reduxSagaThrottle: Readonly<IReduxSagaState>
-}