Perhaps you should try some spelling variations:
optical communication » optical communications, optic communication, political communication
communication model » communication media
development plan » development plans, development planning, development policy
sem development » term development, team development, item development
plan african » pan african, plan africa, class african
4 optical » 14 optical, _ optical, 4 optimal
model sem » model set, model sbm, model sm
gap 4 » gap _, gap a

You may be able to get more results by adjusting your search query.

• Adding a wildcard symbol may retrieve word variants: technologies _ information gap 4 optical communication model sem development plan african.*.