jwenting said:

I've had more than a few answers deleted and downvoted for referencing printed books, complete with page numbers, ISBN (if available), etc. because "it's not online so we can't verify it". Ditto with references to museum collections, mentioning the museum in question where the objects can be found.

(Although I can't find examples of this downvoting for referencing an offline source.)

Do we require references to be available online?


There was never an issue with citing offline sources, they are certainly allowed. There was occasionally an issue though with users citing books in a very, very broad way.

Especially for long resources like books, answers should refer to specific parts when citing and ideally quote an appropriate excerpt.

What is problematic is if a user writes a long answer, and then just adds a book as a reference and claims that their answer is supported by the book, without providing any details. This is not a useful way to reference a post, as it would require reading the entire book to validate if the answer is actually supported by the book.

So while I think that offline sources like books are certainly acceptable, I do expect users to cite specific pages or chapters of a book, and not just the entire book.

  • Completely agree.
    – user5582
    Dec 17 '13 at 10:10
  • When citing a whole book, the burden is really too much to make it a usable reference: one needs to read the book to see if it supports the answer, or if it is applicable to the answer, and this determination is almost entirely subjective; then they need to verify the sources of the book, if any, and especially relevant sources, and this is very time consuming. In other words there are three reasons why whole books are not good: too long to read, too hard to verify, and not objectively relevant.
    – Sklivvz
    Dec 17 '13 at 12:39

We follow the same guidelines as Wikipedia in this regard:

  • Access to sources:

    Some reliable sources may not be easily accessible. For example, some online sources may require payment, while some print sources may be available only in university libraries or other offline places. Do not reject sources just because they are hard or costly to access. If you have trouble accessing a source, others may be able do so on your behalf.

  • Offline sources:

    [T]here is no distinction between using online versus offline sources. In fact, many great sources are only available offline.


    [Relying] extensively on online sources is not surprising, considering the relative ease of accessing such materials. There is also an additional advantage of using online sources, because it allows all users to evaluate the source and its value to the article. However, this reliance on online sources can lead to recentism, where most articles and content are from the internet era.

  • Reliable sources: cost

    Reliable sources must be able to be verified. This does not mean that any particular person at any given moment must be capable of verifying them.

    1. Verifiable sources may have time restrictions (only accessible between 10am and 4pm in a particular time zone).

    2. Verifiable sources may have location restrictions (only available at one archive, museum, repository, or only available within a certain country or geographical area).

    3. Verifiable sources may have cost restrictions (the purchase of a book, journal article, magazine, newspaper, or the Interlibrary Loans or Document Delivery costs associated with them, access to a museum costs, costs of entry to paid archival services).

    4. Verifiable sources may have technical or personal restrictions (written in languages other than English, on websites that require a certain software, available on a type of media that requires the reader to have a certain type of technological appliance to access it)

Making an offline source useful for readers:

  • Provide of full bibliographic information.
  • Providing identifiers such as an ISBN, OCLC number, Open Library number or similar can help others locate physical copies, as cataloguing data can often vary from one library to another.
  • Cite as specifically as possible, preferably down to the page number in the case of a book.
  • Quote the relevant material in your answer.

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