• https://dspace.ube.edu.ec/items/ff7939b8-2dc8-4002-a340-040a9f96738a
• https://dspace.ube.edu.ec/items/ff7b4b7e-7c40-461e-adac-0cd0a3eda27b
• https://dspace.ube.edu.ec/items/ffd723b7-8f3d-48d5-9356-77e99c9c3c70
• https://dspace.ube.edu.ec/items/fff69c5c-4da2-4817-a31e-0a9e6fef2984