KnowraTube lemmaLinked fromLinked fromThe 4 pages that link to Tube lemma, each with the reason it gives.All 4Related 4Compact spaceRelated: It supplies a key step in proving compactness results for product spaces.Open coverRelated: Its proof uses finite subcovers to control an entire compact fiber.Product topologyRelated: It uses product-open neighborhoods to transfer compactness from a factor to a product.Tychonoff's theoremRelated: It supplies a direct proof for products with a compact factor.