400. That’s an error.

Google cannot redirect you to http://zmath.impa.br/cgi-bin/zmen/ZMATH/en/quick.html?first=1&maxdocs=3&bi=0138+10207&type=pdf&bi_op=contains&format=complete because the request was invalid.

This might be because the link was created a long time ago. Try your search again on Google. That’s all we know.