Possible Introduction of reCaptcha by Springer?

[chaosAD]

Hi all,

I am not reporting an issue about the code, but just to share about what I encountered yesterday. While I was amending and testing the code, I was greeted with reCAPTCHA page. When I tried downloading manually, it indicated that the server was overloaded. However, the reCAPTCHA disappeared after about an hour or so later.

I believe Springer are aware that their free e-books are being downloaded by bots and has already put in place the reCAPTCHA, waiting to appear when overloaded with suspicious downloads. If we don't play nice, I reckon they might permanently enforce the reCAPTCHA downloading policy. Once that happens, then that will be the end to this automated download.

[renanxcortes]

This relates to #113 and renanxcortes/springerQuarantineBooksR#53.