[14] FHWA. Design pamphlet for the determination of design subgrade in support of the 1993 AASHTO guide for the design of pavement structures, No FHWA-RD-97-083. Federal Highway Administration, 1997, p. 16. [En línea]. Disponible en: https://www.fhwa.dot.gov/publications/research/infrastructure/pavements/ltpp/97083/97083.pdf