Complex sentence: Construction of the remaining two units, Mochovce-3 and Mochovce-4, began in 1985 but was halted in 1991 due to a lack of funds.
Split into simpler sentences: Construction of the remaining two units, Mochovce-3 and Mochovce-4, began in 1985. However, construction was halted in 1991 due to the lack of funds.