Some linguists restrict the double-dot subscript ⟨◌̤⟩ to murmured sonorants, such as <answer>vowels and nasals</answer>, which are murmured throughout their duration, and use the superscript hook-aitch ⟨◌ʱ⟩ for the breathy-voiced release of obstruents.
What are, according to the text, murmured for their duration?
vowels and nasals