Typical defining relative clause with a preposition

The agency is bankrupt We bought our tickets from it The agency from which we bought our tickets is bankrupt The agency which/that we bought our tickets from is bankrupt The agency we bought our tickets from is bankrupt

Typical non-defining relative clause with a preposition

Which must be used in non-defining clauses; that is not possible: The Acme Travel Agency has opened four new branches Our company has been dealing with it for several years. The Acme Travel Agency, with which our company has been dealing (or which our company has been dealing with) for several years, has opened four new branches

1.37 'Whose' + noun with a preposition

Whose + noun can be used as the object of a preposition. The preposition may come before whose or at the end of the clause: He is the man from whose house the pictures were stolen He is the man whose house the pictures were stolen from

1.37.1 Typical defining relative clause using 'whose' with a preposition In 1980 he caught a serious illness He still suffers from its effects In 1980 he caught a serious illness from whose effects he still suffers (or the effects of which he still suffers from).