AI 14R, M14P, M14PF engines & most likely the Chinese versions.
YAK-3 relevant to YAK-9 also
3 short video clips of the YAK 55 in vertical Lomcovak, torque roll falling and flying away and shallow climbing lomocovak flown by Uli Dembinski, German team member.
L-29 Delfin manufactured by Aero Vodochody, Czechoslovakia (as was)
L-39 Albatross manufactured by Aero Vodochody, Czechoslovakia
Personal profile of Mark Jefferies written in 1995