Relative clauses can be introduced by these relative pronouns:
Who/whom/whose which that.
The choice between who and whom can sometimes cause problems. The traditional rules are these:
 Use who as the subject of the verb:
Any members who find themselves in the Adelaide area can be assured of a warm welcome there.
 Use of whom as the object of the verb:
The God whom we worship.
 Use whom after prepositions:
To whom have you complained?
These rules should still be followed in formal writing. Increasingly, however, who is replacing whom in speech and less formal writing.
For example:
They had to say who they supported.
Instead of
They had to say whom they supported.
And
Currently, most people won’t go and see a band who they haven’t heard of.
Instead of
Currently, most people won’t go and see a band of whom they haven’t heard.
For Scientific english editing and Medical Writing Services visitwww.manuscriptedit.com