Leaflet control window is not a function

Question

I trying to add a leaflet control window to my map, but i get an error in the console of browser. The error is in console is:

Uncaught ReferenceError: L is not defined
at L.Control.Window.js:1
Uncaught TypeError: L.control.window is not a function
at visor.js:16

I copied the folder of plugin to my public html, and added the url to css and js file of plugin in my index.html.

My code is:

var win = L.control.window(mapa, {title: 'Hello world!', content: 'This is my first control window.'})
    .show();