Nested unordered lists including ul tags in each nest

• Top-level list item 1
• Top-level list item 2
  • Secondary-level list item 1
  • Secondary-level list item 2
• Top-level list item 3

Nested unordered lists including ul tags only for the top level

(And of course it doesn't validate.)

• Top-level list item 1
• Top-level list item 2
• Secondary-level list item 1
• Secondary-level list item 2
• Top-level list item 3