Aijmer, K. 1996, I think - An English Modal Particle. - Modality in Germanic Languages, Berlin, 1-47.
Brinton, L. J. 1996, Pragmatic Markers in English. Grammaticalization and Discourse Functions, New York-Berlin.
Brinton, L. J. 2001, From Matrix Clause to Pragmatic Marker. The History of Look-Forms. - Journal of Historical Pragmatics 2, 177-199.
doi:10.1075/jhp.2.2.02bri
Bybee, J. L. 1985, Morphology. A Study of the Relation between Meaning and Form, Amsterdam-Philadelphia (Typological Studies in Language 9).
Bybee, J., Hopper, P. 2001, Introduction to Frequency and the Emergence of Linguistic Structure. - Frequency and the Emergence of Linguistic Structure, Amsterdam-Philadelphia (Typological Studies in Language 45), 1-24.
Dehé, N. 2009, Clausal Parentheticals, Intonational Phrasing, and Prosodic Theory. - Journal of Linguistics 45, 569-615.
doi:10.1017/S002222670999003X
Dehé, N., Wichmann, A. [forthcoming], Sentence-Initial I think (that) and I believe (that). Prosodic Evidence for Use as Main Clause, Comment Clause and Discourse Marker. - Studies in Language.
Erelt, M., Kasik, R., Metslang, H., Rajandi, H., Ross, K., Saari, H., Tael, K., Vare, S. 1993, Eesti keele grammatika II. Süntaks. Lisa: kiri, Tallinn.
Ford, C. E., Thompson, S. A. 1996, Interactional Units in Conversation. Syntactic, Intonational, and Pragmatic Resources for the Management of Turns. - Interaction and Grammar, Cambridge (Studies in Interactional Sociolinguistics 13), 134-184.
Hennoste, T. 2004, Et-komplementlause kesksete põhiverbide funktsioonid eestikeelses vestluses. - KK, 504-523, 590-609.
Hopper, P. 1987, Emergent Grammar. - Berkeley Linguistics Society. Papers of the Thirteenth Annual Meeting, Berkeley, 139-157.
Jackendoff, R. S. 1972, Semantic Interpretation in Generative Grammar, Cambridge, MA-London.
Kaltenböck, G. 2005,Ê Charting the Boundaries of Syntax. A Taxonomy of Spoken Parenthetical Clauses. - Vienna English Working Papers 14, 21-53.
Karlsson, S. 2005, Modalitet i interaktion - en studie av jag tycker och tycker jag. - Samtal och Grammatik, Lund, 119-138.
Keevallik, L. 2003, From Interaction to Grammar. Estonian Finite Verb Forms in Conversation, Uppsala (Acta Universitatis Upsaliensis. Studia Uralica Upsaliensia 34).
Kärkkäinen, E. 2003, Epistemic Stance in English Conversation. A description of its Interactional Functions, with a Focus on I think, Amsterdam- Philadelphia.
Linell, P. 1998, Approaching Dialogue. Talk, Interaction and Contexts in Dialogical Perspectives, Amsterdam-Philadelphia.
Longman Grammar of Spoken and Written English, Harlow 1999.
Rouchota, V. 1998, Procedural Meaning and Parenthetical Discourse Markers. - Discourse Markers. Descriptions and Theory, Amsterdam-Philadelphia (Pragmatics & Beyond NS 57), 97-126.
Scheibman, J. 2000, I dunno… Usage-Based Account of the Phonological Reduction of don't in American English Conversation. - Journal of Pragmatics 32, 105-124.
doi:10.1016/S0378-2166(99)00032-6
Thompson, S. A. 2002, "Object Complements" and Conversation. Towards a Realistic Account. - Studies in Language 26, 125-164.
doi:10.1075/sl.26.1.05tho
Thompson, S. A., Mulac, A. 1991a, The Discourse Conditions for the Use of the Complementizer that in Conversational English. - Journal of Pragmatics 15, 237-251.
doi:10.1016/0378-2166(91)90012-M
Thompson, S. A., Mulac, A. 1991b, A Quantitative Perspective on the Grammaticalization of Epistemic Parentheticals in English. - Approaches to Grammaticalization, Vol. 2. Focus on Types of Grammatical Markers, Amsterdam-Philadelphia (Typological Studies in Language 19), 313-339.
Traugott, E. C. 1980, Meaning-Change in the Development of Grammatical Markers. - Language Sciences 2, 44-61.
doi:10.1016/S0388-0001(80)80004-0
Traugott, E. C. 1989, On the Rise of Epistemic Meaning in English. An Example of Subjectification in Semantic Change. - Language 65, 31-55.
doi:10.2307/414841
Traugott, E. C. 1995, Subjectification in Grammaticalization. - Subjectivity and Subjectivization. Linguistic Perspectives, Cambridge, 31-54.
Traugott, E. C. 1997, Subjectification and the Development of Epistemic Meaning. The Case of promise and threaten. Modality in Germanic Languages. Historical and Comparative Perspectives, BerlinNew York (Trends in Linguistics, Studies and Monographs 99), 185-210.
Tsui, A. B. M. 1991, The Pragmatic Functions of I don't know. - Text 11, 607-622.
doi:10.1515/text.1.1991.11.4.607
Waltereit, R. 2002, Imperatives, Interruptions in Conversation, and the Rise of Discourse Markers. a Study of Italian guarda. - Linguistics 40, 987-1010.
doi:10.1515/ling.2002.041