APA Style

Merriam-Webster, I, (, C, I, C, W, T, E, O, M. ([Check inside — vari). Webster’s Dictionary for Students (Sixth Edition). Springfield, MA, USA: Federal Street Press (or Merriam-Webster, depending on edition).

MLA Style

Merriam-Webster, Inc., (or:, Created, In, Cooperation, With, The, Editors, Of, Merriam-Webster). "Webster’s Dictionary for Students". Sixth Edition Springfield, MA, USA: Federal Street Press (or Merriam-Webster, depending on edition), [Check inside — vari. BOOK.