Relative pronouns can function as objects in both restrictive and non-restrictive clauses. If the pronoun refers to a human, then the word “whom” is used. When the pronoun refers to a non-human thing, in which, where, and when are used.

The book in which these concepts are first described was published in 2010.

The relative pronoun where is used when a physical location is being referred to. Where is also sometimes used instead of in which when referring to a printed source. This usage is not incorrect, although it is less formal.

Runic artefacts can appear in a wide variety of materials, in contrast to rune stones where letters are carved onto naturally resistant material.

The book where these concepts are first described was published in 2010.

The relative pronoun when can be used if a time period is being referred to, although in which can also be used.

Interpretations of cultures are inevitably influenced by the historical period when they were made.