http://book.klll.cc/ebooks/subject/14337.opds 2025-09-21T17:53:53Z Books about Variable stars (sorted by popularity) Free eBooks since 1971. Project Gutenberg https://book.klll.cc webmaster@gutenberg.org https://book.klll.cc/gutenberg/favicon.ico 25 1 2025-09-21T17:53:53Z https://book.klll.cc/ebooks/35613.opds A Plan for Securing Observations of the Variable Stars Edward C. Pickering