González-Guzmán, Jorge. 2018. “Global Stability Results on an Epidemiological Model With a Core Group (a Note on the Paper "Local Stability Results on a Model for Typhoid Fever With a Core group")”. Proyecciones (Antofagasta, On Line) 13 (1):09-17. https://doi.org/10.22199/S07160917.1994.0001.00003.