OpenLayers 3 restrict map to an area

I want to restrict the OpenLayers 3 heatmap-earthquakes examle to show only Europe.

I have:

var raster = new ol.layer.Tile({
  source: new ol.source.Stamen({
    layer: 'toner-background'

  })
});

var map = new ol.Map({

  layers: [raster, vectorLayer],
  target: 'map',
    view: new ol.View({
        projection: 'EPSG:3857',
        center: [0, 0],

        maxZoom: 9,
        minZoom: 0,
        zoom: 4
  })
});

Let`s say that the points:

var point1 = new ol.geom.Point(ol.proj.transform([-20.000000, 28.000000], 'EPSG:4326', 'EPSG:3857'));
var point2 = new ol.geom.Point(ol.proj.transform([50.000000, 73.000000], 'EPSG:4326', 'EPSG:3857'));

are the bounds of Europe, how can I restrict the map view only between the two point?