Frediani, B., Rossini, M., Adami, S., Bianchi, G., Di Munno, O., Sinigaglia, L., Antonelli, M. and Minisola, G. 2006. Study of vitamin D status of rheumatoid arthritis patients Rationale and design of a cross-sectional study by the osteoporosis and metabolic bone diseases study group of the Italian Society of Rheumatology (SIR). Reumatismo. 58, 4 (Dec. 2006), 314–318. DOI:https://doi.org/10.4081/reumatismo.2006.314.