The present invention provides a method of producing oligomers of olefins, comprising reacting olefins with a catalyst under oligomerization conditions. Said mixture consists of a fraction of heavy hydrocarbons dissolved in mud in gaseous form. The AED also determines whether the pads have been removed from a liner and if so, issues a pad application prompt. The testing means is arranged to generate the test signals, I1, 12 and to apply them via a coupling circuit 23, 23a to the electrodes. Respective notches receive the bridge of the wearer’s nose. The clutch actuators are operable to actuate a plurality of torque transmitting devices and the synchronizer actuators are operable to actuate a plurality of synchronizer assemblies.