How the choice of cascode bias voltage?
For Q9:
All currents are equal in P-channel current mirror. Let's notice, that Vgs=Vt+Vdsat.
Hence it is necessary to make Vgs (Q9) =Vgs (Q3c or Q4c) +Vdsat=Vt+2Vdsat
The first line factor is 2²=4.
For Q11:
The currents of transistors Q5 and Q6 are double currents concerning other currents. The saturation voltage is equally Vdsat2=√2 Vdsat for a double current
Hence it is necessary to make
Vgs (Q11) =Vgs (Q1c or Q2c) +Vdsat2=Vt + (1+√2) Vdsat
Second line factor is (1+√2)²=1+2*√2+2=3+2*√2.