Isea Raúl, Mayo-García Rafael, Analysis of Covid-19 Using A Modified SEIR Model To Understand The Cases Registered in Singapore, Spain, And Venezuela, Journal of Model Based Research, Volume 1, Issue 4, 2022, Pages 13-22, ISSN 2643-2811, https://doi.org/10.14302/issn.2643-2811.jmbr-22-4258. (http://jcci-clinicalarticles.infojmbr/article/1864) Keywords: Covid-19; SEIR; Mantissa; Dynamics; Spain; Singapore; Venezuela