The mhequ style file simplifies creating multi-column equation environments and tagging equations therein. It supports sub-numbering of blocks of equations, such as (1.2a) and (1.2b), references to each equation individually (1.2a) or to the whole block (1.2). The labels can be shown in draft mode. The default behaviour is to show an equation number if and only if the equation actually has a label, which reduces visual clutter.