How to get this expression for LC impedance?

In the paper:Analysis and design of Injection locked LC dividers for quadrature generation,JSSC 2004. I can not get the expression(please see the attachment) for the impedance of LC element.

Woul you please give me any advice?
Thank you very much.

It's the expression of the Impedence wrote on Q rather than on L&C.
It's a known, general form, and it's valid regarless the resonant circuit topology.
Of course the Q expression will change as resonator topology.
Q≡Reactive Power / Dissipative Power
To find Q as function of ω, you may know L & C