Total impedance at resonance, $Z_{T_{p}}$
The total impedance at resonance is now defined by
$$ Z_{T_{p}} \appro R_s || R_p = R_s || Q_l^2 R_l $$
For an ideal current source ($Rs \nfty Ω$), or if $R_s >> R_p$, the equation
reduces to
$$ \bbox[10px,border:1px solid grey]{Z_{T_{p}} \appro Q_l^2 R_l} $$