"whose belief" is correct and can be used in written English
You can use it whenever you need to refer to something that someone believes. For example, "Many people have strong moral convictions, whose belief systems shape their behavior."
There are those whose belief is strong and those whose unbelief is equally unyielding.
Podro was someone whose belief in the life of the mind ran very deep.
But he has architectural heroes, too, like the critic Ian Nairn, whose belief in the spirit of place Meades champions.
It is a run the NRL, whose belief in parity is near-spiritual, hopes will continue this weekend.
Gersten, a Jewish lawyer whose belief in the First Amendment overcomes her personal revulsion for Cooper, takes the case.
Funerary architecture is produced by societies whose belief in the afterlife is materialistic and by individuals who want to perpetuate and symbolize their temporal importance.
As someone whose belief in sport's redeeming qualities is ebbing away, being proved wrong will be a relief and a privilege.
Unlike leaders of the Taliban, whose belief in public relations was minimal and who anyway regarded westerners as inherently hostile, Mr Masoud was welcoming.
Döllinger was a brilliant scholar whose embrace of modern historical criticism and whose belief in religious freedom brought him into conflict with papal policy.
It was sufficient for the EU, whose belief in legally enforceable international agreements is shared by the Brazilians, to claim success.
This is a minority critical view – and expressing it has revealed to me that there are commenters whose belief in diversity of opinion exists in theory only.
