For the daily kanji, I used a number of sources. The principle sources are from the Electronic Dictionary Research and Development Group (EDRG). The driving force behind EDRG is Jim Breen.

The dictionary program I use (Lindesay Electric's Word Look Up) relies on the work of EDRG.

I also consult the following dictionaries:

Spahn, M. & Hadamitzky, W. 1998 The Learner's Kanji Dictionary. Tuttle Publishing, Boston

Takebayashi, S (Ed.) 1996 The Kenkyusha English-Japanese Learner's Pocket Dictionary Kenkyusha, Tokyo