**Proof by intimidation** Trivial!

**Proof by cumbersome notation** The theorem follows immediately from the fact that

**Proof by inaccessible literature** The theorem is an easy corollary of a result proven in a hand-written note handed out during a lecture by the Yugoslavian Mathematical Society in 1973.

**Proof by ghost reference** The proof my be found on page 478 in a textbook which turns out to have 396 pages.

**Circular argument** Proposition 5.18 in [BL] is an easy corollary of Theorem 7.18 in [C], which is again based on Corollary 2.14 in [K]. This, on the other hand, is derived with reference to Proposition 5.18 in [BL].

**Proof by authority** My good colleague Andrew said he thought he might have come up with a proof of this a few years ago...

**Internet reference** For those interested, the result is shown on the web page of this book. Which unfortunately doesn't exist any more.

**Proof by avoidance** *Chapter 3:* The proof of this is delayed until Chapter 7 when we have developed the theory even further.*Chapter 7:* To make things easy, we only prove it for the case *Appendix C:* The formal proof is beyond the scope of this book, but of course, our intuition knows this to be true.