The top four useful sources are the following:
1) Full details about the growing number of voluntary sustainability standards can be found on the ITC Sustainability Map
2) ISEAL Alliance maintains a database of publications on impacts of certification.
3) Look at the Sustainable Development Solutions networks on Sustainable Agriculture & Food Systems; and on Redefining the Role of Business.
4) Useful courses available at the SDG Academy; see for example "Globalization: past and future".