Authors deliberately reject a single preferred model; each industry gets whichever of QQCD/Fourier survives the specification search, so there is no headline point estimate. The QQCD estimates are favored where identifiable (more precise, satisfy concavity). || 'The comparison of models need not involve choosing a single preferred model for all industries.' (p.85) and 'the combined approach yields more precise estimation of the substitution elasticities' (p.86)
Mountain, D. C., and C. Hsiao (1989): “A Combined Structural and Flexible Functional Approach for Modeling Energy Substitution.” Journal of the American Statistical Association 84(405), 76-87