Targeting Multi-site Businesses

As a geographical representative, I know how to identify ideal target accounts using internal tools such as Salesforce, cross referencing that data with external databases such as Data Axle (formerly ReferenceUSA/Data.com) to be sure I have the whole haystack in my database.

One particular type of client, however, slips through this methodology, in part due to the limitations of the tools used, multi-site business.

There has to be a better way of identifying these businesses within a geo. short of simply clicking 'locations' on the individual company's website, as one researches companies. Hoping this brain trust, and one of you sales savages can bring me to the promised land of finding these types of establishments. Thanks in advance.