1. Conventions. The book is divided into 16 chapters, each subdivided into sections numbered in order (e.g. chapter 12, section 3 is numbered 12.3).

Within each chapter results (Theorems, Propositions or Lemmas) are labelled by the chapter and then the order of occurrence (e.g. the fifth result in chapter 3 is Proposition 3.5). The exceptions to this rule are: sublemmas which are presented within the context of the proof of a more important result (e.g. the proof of Theorem 2.2 contains Sublemmas 2.2.1 and 2.2.2); and corollaries (the corollary to Theorem 5.5 is Corollary 5.5.1).

We denote the end of a proof by ▪.

Finally, equations are numbered by the chapter and their order of occurrence (e.g. the fourth equation in chapter 5 is labelled (5.4))

2. Notation. We shall use the standard notation: ℝ to denote the real numbers; ℚ to denote the rational numbers; ℤ to denote the integer numbers; ℕ to denote the natural numbers; and ℤ+ to denote the nonnegative integers. We use the convenient convention that: ℝ/ℤ = {x + ℤ : x ∈ ℝ} (which is homeomorphic to the standard unit circle); ℝ2/ℤ2 = {(x1, x2) + ℤ2 : (x1, x2) ∈ ℝ2} (which is homeomorphic to the standard 2-torus); etc. However, for x ∈ ℝ we denote the corresponding element in ℝ/ℤ by x (mod 1) (and similarly for ℝ2/ℤ2, etc.).