The preterite with regular and stem-changing verbs

Spanish Proficiency Exercises- Preterite Tense: https://www.laits.utexas.edu/spe/int23.html?v=g
Spanish Grammar in context-Preterit: http://grammar.spanishintexas.org/verbs/preterite/

Pretérito indefinido regular: https://www.youtube.com/watch?v=mvv6SOVWNFw
El pretérito indefinido: https://www.youtube.com/watch?v=cW06yDbEPA8
Pretérito indefinido – verbos que cambian la g/j: https://www.youtube.com/watch?v=MLpDwNnXMg8
Pretérito indefinido – verbos que cambian la i/y: https://www.youtube.com/watch?v=5826tEOHmfc