Amstex sample bold greek
Using Bold Greek Letters in AmSTeX
Bold Greek letters are available using the \boldsymbol macro, which needs to be enabled by calling \loadbold in the preamble.
\documentstyle{amsppt} \loadbold \document Let $\boldsymbol\alpha$ be a vector. Call it $\boldsymbol\beta$. \enddocument
(Note that this is not to be taken as an example of good mathematical exposition.)