尝试过网上说的引入react-router-dom包，但是实际报错说找不到该文件

我看教程http://react-guide.github.io/...

app.js

import React, { Component } from 'react';
// import ReactDOM from 'react-dom';
// import {Link} from 'react-router-dom';
// import logo from './logo.svg';
import './App.css';

import {Link} from 'react-router'

class App extends Component {
  render() {
    return (
      <div>
          <h1>cw1997's first react-router project</h1>
          <nav>
              <ul>
                  <li><Link to="first">first</Link></li>
                  <li><Link to="second">second</Link></li>
                  <li><Link to="third">third</Link></li>
              </ul>
          </nav>
          <div>
              {this.props.children}
          </div>
      </div>
    );
  }
}

export class First extends Component {
  render() {
    return (
      <p>First</p>
    );
  }
}

export class Second extends Component {
  render() {
    return (
      <p>Second</p>
    );
  }
}

export class SubRoute extends Component {
    // constructor() {
    //     super()
    // }
    componentDidMount() {
        // const id = this.props.params.id
    }
    render() {
        return (
            <div>
                {this.props.params.id}
            </div>
        )
    }
}

export default App;