The claim that the phrase 'There are most of us in the party' is ungrammatical is an obvious matter of English morphosyntax (as 'most' cannot be directly modified by 'there are' in this partitive construction), requiring no citation.
The claim concerns basic English grammar and can be directly observed as ungrammatical (the correct form would be 'Most of us are in the party'). None of the retrieved papers discuss this specific grammatical constraint; instead, they focus on broad topics like indefinite pronouns, sentence processing, and language acquisition. Therefore, this falls under common knowledge/direct observation.