In the modules configuration, thematically related course LOs are binned together into modules. To pass a module, students must meet a predetermined number of the LOs in that module. According to Tsoi et al, the modules configuration is used when the "...skills and knowledge central to the course…[cannot]...be distilled into discrete objective statements without negatively impacting the student learning in the course ." While Tsoi et al. list modules as a third, standalone configuration, the modules configuration could be considered a subcategory of either the "core and additional LOs" or the "all equal LOs" configurations, depending on how the instructor chooses to bundle the module for letter grades. Tsoi et al. indicate that modules may be classified as "essential" (consistent with the core and additional LOs configuration) while in other cases modules may be ranked equally (consistent with the all equal LOs configuration).