Original sentence: Chang's contribution to heterodox economics started while studying under Robert Rowthorn, a leading British Marxist economist, with whom he worked on the elaboration of the theory of industrial policy
Edited sentence: Chang's contribution to heterodox economics started while studying under Robert Rowthorn, a leading British Marxist economist, with whom he worked on the elaboration of the theory of industrial policy, a middle-way between central planning and the unrestrained free-market