Singularidades de ecuaciones diferenciales

New channel Instituto de Matemáticas de la UNAM: title sample judged 'whole' (This is an academic math institute's seminar/lecture archive with near-uniform research-level and expository mathematics); passed a second screen for sellers/exam-prep/re-uploads; 0 of 3 sampled transcripts showed teaching, 0 not; titles picked one by one, checked strictly; oEmbed verified.