In terms of the search strings
Some of the six categories where sub-divided to show with more clarity and detail the lean-green research avenues petiole the articles had explored. The numbers attached (squares) to the categories and sub-categories represent a cross reference to the articles included in Table 1. For example, Azevedo et al. (2012) is article number 5 in Table 1, and has been linked to the sub-categories ‘environmental’, ‘sustainability’, ‘supply chain’, ‘production/manufacturing/industrial systems & processes’ and ‘manufacturing’.