These sources are excerpts from two letters written by Warren E. Buffett to the limited partners of Buffett Partnership, Ltd. (BPL), summarizing the partnership’s investment performance during 1968. The July 11, 1968 letter reports an "unusually good" 16.0% gain for the first half of the year, significantly outperforming the Dow-Jones Industrial Average's 0.9% gain, though Buffett cautions against unwarranted excitement due to concentrated investments. The second letter, dated January 22, 1969, details the full year's spectacular success, achieving an overall gain of 58.8% against the Dow's 7.7%, attributing the extraordinary result to one "simple but sound idea" within the Generals–Private Owner category. Both communications include extensive tables comparing BPL’s historical results and annual compounded rates of return against the Dow and various major investment funds, highlighting BPL's consistent superiority. Buffett also expresses growing concern about the "chain-letter type stock-promotion vogue" prevalent in the market, noting that this mania creates both opportunities and challenges for finding fundamentally attractive investments.