1991ApJ...371..607S
1991ApJ...371..607S
1991ApJ...371..607S
1991ApJ...371..607S
1991ApJ...371..607S
1991ApJ...371..607S
1991ApJ...371..607S
1991ApJ...371..607S
1991ApJ...371..607S
1991ApJ...371..607S
1991ApJ...371..607S
1991ApJ...371..607S
1991ApJ...371..607S
1991ApJ...371..607S