WEBSITES:
Sea Hermit Blog ~ Tom Rizzo
This particular blog was created by a fellow float collector.  He specializes in European floats & has researched their history extensively.  There is a lot of great information & photographs on the blog.
Best Norwegian ~ Info on European Glass Fishing Floats
This website offers travel information on Norway, but there is a page dedicated to glass fishing floats.  A float collector friend of mine, Per Einar Gunnarsen, has done extensive research & traveled through Norway finding new marks & digging up lot of historical information.
**This site offers detailed information on how to replace the nets on floats.
Norway Float ~ Info on European Glass Fishing Floats
This website also offers a lot of historical information & photographs about European glass fishing floats.
BOOKS:
The following books are great references for information on the history of glass fishing floats, various marks, shapes & uses.
Beachcombing for Japanese Glass Floats
  Author:  Amos Wood
Glass Ball:  A Comprehensive Guide for Oriental Glass Fishing Floats Found on Pacific Beaches
Author:  Walt Pich
Glass Ball Marks:  A Field Guide to Identify Characters on Oriental Glass Fishing Floats
  Author:  Walt Pich
Glass Ball Shapes
  Author:  Walt Pich
**Periodically, I will have the books by Walt Pich for sale in my Etsy shop.
CONTACT INFORMATION:
If you would like to contact me about glass fishing floats, I would be happy to try to answer your questions, or I can refer you to someone that might be able to help.  I do get a lot of messages, so it might take me a while to reply.  Thank you!
Glass Float Junkie E-Mail