Syndicate Wars - PC Eurocorp levels

SW levels description and walkthrough:

There are 20 EuroCorp e-mail messages. Some, however, have multiple objectives, which must be achieved in different cities. When you count all these cities, there's a total of 34 missions. A unique identification for every mission is the REF number from the e-mail icon, followed by the location.

REFS 0 to REF 3 are mere trainer-missions.
REFS 4 to REF 10 are tougher, but still not too difficult.
REFS 11 to REF 15 become more challenging, and are quite difficult.
REFS 16 to REF 19 are the hardest missions of the game.
REF 20 is the last mission and is shared by EuroCorp and the Church. It's not really difficult, but you have to win three missions in a row, because you don't have the opportunity to save in between.