The  ( 1 + Q )^2  Method  (also known as the Resistance Method) is applied in the slides below to the Resonant pi-Network, commonly used  as the output impedance matching network for vacuum tube RF power amplifiers.  There, the typical choice is made for a high-Q, narrow bandwidth response.  The same formulas are beneficial for lower-Q, wider bandwidth situations.

Formulas resulting from the method appear in several references, but perhaps the best tutorial is the 3-part series Simplified Design of Impedance Matching Networks by George Grammer in the 1957 March, April and May issues of QST.  They are available from the World Radio History Archive website  here ,  here ,  and  here .

Pi-network formulas have been published, for example, in the  1967 EIMAC/Varian publication  Care and Feeding of Power Grid Tubes by Robert I. Sutherland, which has been available here .   Also see the Motorola/Freescale/NXP application notes AN721, available here ,  and AN267 here .

The One Plus Q Squared approach was popular at Collins Radio, and with Arthur Collins in particular.   See the interesting anecdote Seeing Was Believing by the late Thomas Cuthbert Jr. at the Engineering and Technology History Wiki site here . 

The slides below blend formulas and Smith Charts with several examples analyzed with circuit simulations in QucsStudio.

A few slides below illustrate a transmission line lumped element LC equivalent network and its relationship to the tank circuit resonant pi.   An L-section is shown to have similar bandwidth.