Helping drag down the group were shares of Clean Energy Fuels ( CLNE ), off about 14.6% and shares of Cosan ( CZZ ) off about 3% on the day. In trading on Thursday, oil & gas refining & marketing shares were relative laggards, down on the day by about 0.8%. Also lagging the market Thursday are aerospace & defense shares, down on the day by about 0.8% as a group, led down by Embraer ( ERJ ), trading lower by about 10.1% and CPI Aerostructures ( CVU ), trading lower by about 6.1%.