Research supported in part by NSF Grants DMS-9504176 and DMS-9800701 σ r Q (u, v)dV for σ r the symbol evaluated at τ = r and dV Haar measure [48,50]. We generalize a result of S. Zelditch [50, Prop.2.1] and show that the microlocal lift satisfies a partial differential equation; the equation is basic to our approach. A second microlocal lift is also considered.the assignment u to Q M (u) is equivariant for the left action on SL(2; R). An integration by parts argument provides a bound for the difference of Q (u, v) and Q M (u) for M large of order O(r −1 ) given uniform bounds for u 2m . The Fejér sum construction provides an alternative to introducing Friedrichs symmetrization, [9,48]. Our initial interest is the microlocal lift of the Macdonald-Bessel functions.The Macdonald-Bessel functions were introduced one-hundred years ago in a paper presented to the London Mathematical Society by H. M. Macdonald [33]. The paper includes a formula for the product of two Macdonald-Bessel functions in terms of the integral of a third Bessel function. We will develop formulas for the microlocal lift from such an identity [31,33].To present our main result we first describe a family of measures on SL(2; R). The square root (the double-cover) of the unit cotangent bundle of H is equivalent to SL(2; R). A geodesic has two unit cotangent fields and four square root unit cotangent fields. The geodesic-indicator measure ∆ αβ on SL(2; R) is the sum over the four lifts of the geodesic αβ of the lifted infinitesimal arc-length element. We further write ∆for the sum over Γ ∞ , the discrete group of integer translations. We consider for t = 2πnr −1 the microlocal lift of K(z, t) = (ry sinh πr) 1/2 K ir (2π|n|y)e 2πinx , and define the distributionfor ∆t = 2πr −1 . We show in Theorem 4.9 that for αβ the geodesic on H with Euclidean center the origin and radius |t| −1 and dV Haar measure then in the sense of tempered distributions Q symm (t)dV is close to π 2 8 ∆ Γ∞( αβ) uniformly for r large and |t| restricted to a compact subset of R + . At high-energy the microlocal lift of a Macdonald-Bessel function is concentrated along a single geodesic. Accordingly, at high-energy the behavior of the microlocal lift of a sum of Macdonald-Bessel functions is explicitly a matter of the space of geodesics and sums of coefficients. We introduce in Chapter 3 a coefficient summation scheme for studying quantities quadratic in the eigenfunction. The scheme provides a positive measure. In particular for (x, t) ∈ R × R + define the distributionfor d t denoting the Lebesgue-Stieljes derivative in t and for convolution inx with the Fejér kernel F N . We use a slight improvement of the J. M. Deshouillers-H. Iwaniec coefficient sum bound [11] and show for a unit-norm automorphic eigenfunction that Ω ϕ,N is a uniformly bounded tempered distributions. In fact for {ϕ j } a sequence of unit-norm automorphic eigenfunctions the sequences {Q(ϕ j , ϕ j )} and {Ω ϕ j ,N } are relatively compact. We consider a weak * convergent sequence and write Q limit = lim j Q...