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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.
- Verifiable sources may have time restrictions (only accessible between 10am and 4pm in a particular time zone).
- Verifiable sources may have location restrictions (only available at one archive, museum, repository, or only available within a certain country or geographical area).
- 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).
- 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)
The costs or difficulties of verifying a source do not impact on its reliability, as long as it can be verified in a reasonable time frame by someone.
Where a source is difficult to verify, or in a language other than English, many editors appreciate the courtesy of supplying the relevant paragraph and ensuring it can be read by English language readers. When sources of equal quality are available the ease of access may be preferred, but if sources of higher quality are difficult to verify, that difficulty alone is not a reason to disregard such sources or replace them with lower-quality ones.
Where a source is difficult to verify, and legal to duplicate or duplicate portions of, produce impressions of, or otherwise make a recording that will allow other editors to verify off the copy, it is a reasonable expectation, but not mandatory, that this be done to assist other Wikipedia editors in verification. Books in the public domain may be uploaded to Wikisource.
Where to get help 
Editors at these projects may be able to help you determine whether a given source supports the material it is alleged to:
- Wikipedia:WikiProject Fact and Reference Check
- Wikipedia:WikiProject Libraries
- Wikipedia:WikiProject Resource Exchange/Resource Request
- Wikipedia:Translators available
Additionally, you can request help from any relevant WikiProjects.