Portela-Gornes , G. M., L. Grimelius, R. Petersson, and R. Bergström. “Enterochromaffin Cells in the Rat Gastrointestinal Tract: Aspects of Factors Influencing Quantification”. Upsala Journal of Medical Sciences, vol. 89, no. 3, Sept. 1984, pp. 189-03, doi:10.3109/03009738409179499.