Ross' π lemma

Ross' π lemma is a result in the field of measure theory, particularly concerning the integration of functions and properties related to measurability. The lemma is often used in situations involving the interchange of limits and integrals. Although it may not be universally recognized by all mathematicians under the name "Ross' π lemma," it is primarily attributed to the work of mathematician A. Ross. In essence, the lemma establishes conditions under which one can exchange limits and integrals for sequences of measurable functions.