[richardpcrowe]

Tiffen: Polarizing Filter Effects
https://post.craigslist.org/manage/723818383/qyp95

Replacement Light Bulbs.com: Filters
http://www.replacementlightbulbs.com/tipsfilters.html#Filters

PSA Journal – Using CPL in combination with a linear polarizing filter
http://findarticles.com/p/articles/mi_m1306/is_1_73/ai_n17154395

Filter Connection – Facts on Filters
http://www.2filter.com/faq/faq.html

DPFWIW – Filter Options for Digital Cameras
http://www.dpfwiw.com/filters.htm#why

Schneider B&W Filters
http://www.schneideroptics.com/filters/bw.htm

Hoya Filters
http://www.thkphoto.com/products/hoya/index.html

Photofilter.com – Filter Information
http://www.photofilter.com/infomap.htm

Digital SLR Photography Tips - Using Photographic Filters
http://www.all-things-photography.com/photographic-filters.html

Photo Secrets Tips – Andrew Hudson
http://www.photosecrets.com/tips.filters.html

Popular Photography – Filters Vs. Photoshop
http://www.photosecrets.com/tips.filters.html

Chroma Software – Photoshop Photographic Filters Plug-in
http://www.chromasoftware.com/photographic_filters.htm