Abstract5.1. Introduction to the unified formulation5.2. Stiffness matrix of a bar and the related fundamental nucleus5.3. Fundamental nucleus for the case of a bar element with internal nodes5.4. FEM and the theory of structure: a four indices fundamental nucleus5.5. The assembly procedure5.6. A unified approach for one-, two- and three-dimensional structures5.7. Beam5.8. DEBBT, TBT and N=1 in unified form5.9. Higher-order models5.10. 1D models with a physical volume/surface-based geometry and pure displacement variables, the Lagrange Expansion class (LE)5.11. Physical volume/surface approach5.12. Lagrange polynomials and isoparametric formulation5.13. LE displacement fields and cross-section elements5.14. Cross-section multi-elements and locally refined models5.15. Plate5.16. CPT, FSDT and N=1 model in unified form5.17. Unified formulation of N-order5.18. 2D models with physical volume/surface-based geometry and pure displacement variables, the Lagrange expansion class (LE)5.19. Physical volume/surface approach5.20. Lagrange expansion model5.21. Extension to multilayered structures5.22. Multilayered structures5.23. Theories on multilayered structures5.24. Unified formulation for multilayered structures5.25. UF in terms of 1×1 secondary nuclei5.26. Discussion on possible best beam, plate and shell diagrams5.27. The mixed axiomatic/asymptotic method5.28. Static analysis of beams5.29. Modal analysis of beams5.30. Static analysis of plates and shells5.31. The best theory diagramReferences