Siegel, C. A., Whitman, C. B., Spiegel, B. M. R., Feagan, B., Sands, B., Loftus, E. V., Panaccione, R., D'Haens, G., Bernstein, C. N., Gearry, R., Ng, S. C., Mantzaris, G. J., Sartor, B., Silverberg, M. S., Riddell, R., Koutroubakis, I. E., O'Morain, C., Lakatos, P. L., McGovern, D. P. B., Halfvarson, J., Reinisch, W., Rogler, G., Kruis, W., Tysk, C., Schreiber, S., Danese, S., Sandborn, W., Griffiths, A., Moum, B., Gasche, C., Pallone, F., Travis, S., Panes, J., Colombel, J., Hanauer, S., & Peyrin-Biroulet, L. (2018). development of an index to define overall disease severity in IBD. Gut, 67(2), 244–254. http://access.bl.uk/ark:/81055/vdc_100137792752.0x00004a