There is no separate symbol for the dental approximant (as in Spanishnada) in the International Phonetic Alphabet, which most scholars transcribe with the symbol for voiced dental fricative, 〈ð〉.
The most common sound represented by the letter r in English is the postalveolar approximant, pronounced a little more back and transcribed more precisely in IPA as 〈ɹ̠〉, but 〈ɹ〉 is often used for convenience in its place. For further ease of typesetting, English phonemic transcriptions might use the symbol 〈r〉 even though the former symbol represents the alveolar trill in phonetic transcription.
The most common alveolar realization of /r/, with a trill [r] being the alternative realization. The more common uvular realizations are a fricative (either voiced [ʁ] or voiceless [χ]) and, more rarely, a trill [ʀ]. See Standard German phonology
Browman, C.P.; Goldstein, L. (1995), "Gestural syllable position in American English", in Bell-Berti, F.; Raphael, L.J., Producing Speech: Contemporary Issues: for Katherine Safford Harris, New York: AIP, pp. 9–33
Cornyn, William (1944), Outline of Burmese Grammar, Supplement to Language, vol. 20 no. 4, Baltimore: Linguistic Society of America
Delattre, P.; Freeman, D.C. (1968), "A dialect study of American R's by x-ray motion picture", Linguistics44: 29–68
Engstrand, Olle (1999), "Swedish", Handbook of the International Phonetic Association, Cambridge University Press, pp. 140–142, ISBN9780521637510
Fougeron, C (1999), "Prosodically conditioned articulatory variation: A Review", UCLA Working Papers in Phonetics97, pp. 1–73
Grønnum, Nina (2003), "Why are the Danes so hard to understand?", in Jacobsen, Henrik Galberg; Bleses, Dorthe; Madsen, Thomas O.; Thomsen, Pia, Take Danish - for instance: linguistic studies in honour of Hans Basbøll, presented on the occasion of his 60th birthday, Odense: Syddansk Universitetsforlag, pp. 119–130
Hallé, Pierre A.; Best, Catherine T.; Levitt, Andrea (1999), "Phonetic vs. phonological influences on French listeners' perception of American English approximants", Journal of Phonetics27 (3): 281–306, doi:10.1006/jpho.1999.0097
Ikekeonwu, Clara I. (1999), "Igbo", Handbook of the International Phonetic Association, Cambridge University Press, pp. 108–110, ISBN9780521637510
Kohler, Klaus (1995), Einführung in die Phonetik des Deutschen, Berlin: Erich Schmidt Verlag