Lessons were produced every day between Nov 2004 and Dec 2005.
Lessons were produced at "easier" and "harder" levels between Apr 2005 and Aug 2006.
2008: Feb | Jan
2007: Dec | Nov | Oct | Sep | Aug | Jul | Jun | May | Apr | Mar | Feb | Jan
2006: Dec | Nov | Oct | Sep | Aug | Jul | Jun | May | Apr | Mar | Feb | Jan
2005: Dec | Nov | Oct | Sep | Aug | Jul | Jun | May | Apr | Mar | Feb | Jan
2004: Dec | Nov