Just a few links related to fT measurement stuff I've been working on lately:

http://www.ewh.ieee.org/r6/scv/eds/slides/20100216-Prasad-SPara_Talk.pdf
http://www.rfcafe.com/references/electrical/s-h-y-z.htm
http://cache.freescale.com/files/rf_if/doc/app_note/AN139A.pdf
http://staff.ee.sun.ac.za/cvanniekerk/amplifiers.htm
http://www.keysight.com/upload/cmc_upload/All/XParam_Active_Hybrid_LoadPull_EuMW2012.pdf?&cc=US&lc=eng
http://www.microwaves101.com/encyclopedias/load-pull-for-power-devices
http://www.aurigamicrowave.com/bm.doc/btseries_20140731a.pdf
https://www.youtube.com/watch?v=N0dLVMoVQSI
http://www.wolfspeed.com/~/media/Files/Cree/RF/Papers%20and%20Articles/ClassJ_RF_Power_Amplifier_with_Wideband_Harmonic_Suppression.pdf