Need help to get external Url of specified track.

[cquezpro]

@thelinmichael @kaaes

Thanks for good library for Spotify Android developer.
I 'v been working on android project by using your library.

btw, I have a problem to get external url of specified sound track.
In your lib, I could find this class that manages tracks.

public class TrackSimple implements Parcelable {
public List artists;
.... .... ....
public Map<String, String> external_urls;
.... .... ....
}
It looks param(external_urls) manages them, but I don't know the Map keys in this param.
If you let me know those keys and values for this param, I 'll be very grateful to you.
Thanks in advance.
Sirius