"a valid source" is a correct and usable phrase in written English.
You can use it when referring to something that has been verified to be accurate or reliable, such as a piece of information or data. For example, "I found the answer to my question in a valid source online".
Your relationship with 'Parrot' looks very promising as a valid source of info from US power circles.
Kitty lies around gurgling and disgorging the food that's put into her and is not a valid source of entertainment, only of love".
Semenya considers herself female because of what she has been told by her family, and this seems like a valid source of explanation to me.
So there is no way to tell whether the answer to a particular DNS query is from a valid source, allowing malicious parties to carry out all manner of attacks.
Many thanks, Update: PR Newswire confirmed to Webuser.co.uk editor Ben Camm-Jones that the release came from "a valid source, one of Phones 4u's comms agencies".
Can situated emotional responses to things be a valid source of knowledge about them (Diamond 1991, Jaggar 1989, Keller 1983, Pitts-Taylor 2013)?
Investigating the use of GPs as a potentially valid source of information also formed an important part of measuring the feasibility of this approach.
A registry is also preferable if only UTD children are being studied (no misclassification, compared to parent report), whereas parent report would be a more valid source for identifying subjects if the primary focus is not UTD children.
But, the by-products obtained in the process of oils' refining, like the deodorizer distillate, contain 15 to 30% unsaponifiable fraction, with a concentration of up to 80% squalene, depending on several factors, representing an economically valid source for squalene.
Most plagiaristic reflexes boil down to lifting the first Wikipedia entry Google regurgitates, and no amount or explaining, lecturing or admonishing will entirely convince students that -- moral considerations aside -- Wikipedia does not qualify as an academically valid source, since it accepts no responsibility for the accuracy of its content.
MSCs are an alternative valid source of cells for cartilage regeneration as they can be easily gained and expanded in vitro without losing their differentiation potential.
