An article in English, based on Vamshidhara's explanation of Sridhara Swamin's invocation to the Bhagavatam: https://www.quora.com/What-is-the-relation-between-Lord-Shiva-and-Lord-Vishnu/answer/Seeker-394?ch=15&oid=1477743765553252&share=e2960cc2&srid=hZ8vi&target_type=answer