R. Altman, Getting the Subtle Distinctions: Should versus Had Better, Studies in Second Language Acquisition, vol.4, issue.01, pp.80-87, 1986.
DOI : 10.1017/S0272263100005854

C. Bache and N. Davidsen-nielsen, Mastering English Grammar, 1997.

C. Berkenfield, Pragmatic motivations for the development of evidential and modal meaning in the construction ???be supposed to X???, Journal of Historical Pragmatics, vol.7, issue.1, pp.39-70, 2006.
DOI : 10.1075/jhp.7.1.03ber

D. Biber, University Language: A corpus-based study of spoken and written registers, 2006.
DOI : 10.1075/scl.23

S. Brandt, Modal Verbs in Danish, C.A. Reitzel, 1999.

J. Coates, The Semantics of the Modal Auxiliaries, 1983.

P. Collins, The modals of obligation and necessity in Australian English, English Corpus Linguistics: Studies in Honour of Jan Svartvik. Longman, pp.145-165, 1991.

P. Collins, Modals and quasi-modals in English. Rodopi, 2009.
DOI : 10.1163/9789042029095

R. Declerck, A Comprehensive Grammar of English, 1991.

I. Depraetere and S. Reed, Mood and modality in English The Handbook of English Linguistics, pp.269-290, 2006.

I. Depraetere and A. Verhulst, Source of modality: a reassessment, English Language and Linguistics, vol.35, issue.01, pp.1-25, 2008.
DOI : 10.2307/455712

URL : https://hal.archives-ouvertes.fr/halshs-00347343

G. Diewald, A basic semantic template for lexical and grammaticalized uses of the German modals, Modal Verbs in Germanic and Romance Languages. John Benjamins, pp.23-41, 2001.

M. Ehrman, The Meanings of the Modals in Present-Day American English The Hague, 1966.

M. A. Halliday, Functional diversity in language, as seen from a consideration of modality and mood in English, Foundations of Language, vol.6, pp.322-361, 1970.

B. Heine, Agent-Oriented vs. Epistemic Modality, Modalityin Grammar and Discourse. John Benjamins, pp.17-53, 1993.
DOI : 10.1075/tsl.32.03hei

E. Hinkel, The use of modal verbs as a reflection of cultural values, TESOL Quarterly, vol.2, pp.325-343, 1995.

L. Hoye, Adverbs and Modality in English, 1997.

R. Huddleston, The verb The Cambridge Grammar of the English Language, pp.71-212, 2002.

E. Kruisinga, A Handbook on Present-Day English. (Part II. English Accidence and Syntax I) Kemink en Zoon, 1925.
DOI : 10.1007/bf01521692

R. Langacker, Subjectification, Cognitive Linguistics, vol.1, issue.1, pp.5-38, 1990.
DOI : 10.1515/cogl.1990.1.1.5

R. Langacker, Descriptive Application, Foundations of Cognitive Grammar, 1991.

P. Larreya, Quelques remarques sur have to et must, Travaux de l'Université de Saint-Etienne, pp.103-121, 1982.

P. Larreya and C. Rivière, Grammaire Explicative De L'Anglais. Pearson Education Limited, 2005.

J. Lyons, Semantics, 1977.

H. Mccallum-bayliss, The modal verbs: univocal lexical items, 1985.

J. Myhill, Change and continuity in the function of the American modals, Linguistics, vol.33, pp.157-211, 1995.

J. Myhill, A. Laura, and . Smith, The Discourse and Interactive Functions of Obligation Expressions, Modality in Grammar and Discourse. John Benjamins, pp.239-292, 1995.
DOI : 10.1075/tsl.32.11myh

H. Narrog, On defining modality again, Language Sciences, vol.27, issue.2, pp.165-192, 1995.
DOI : 10.1016/j.langsci.2003.11.007

R. Nordlinger and E. Closs-traugott, Scope and the development of epistemic modality: evidence from ought to, English Language and Linguistics, vol.33, issue.02, pp.295-317, 1997.
DOI : 10.2307/414841

. Nuyts, Epistemic Modality, Language and Conceptualisation. A Cognitive-Pragmatic Perspective, John Benjamins, 2000.
DOI : 10.1075/hcp.5

. Nuyts, The modal confusion. On terminology and the concepts behind it, Modality: Studies in Form and Function. Equinox, pp.5-38, 2005.

F. R. Palmer, Modality and the English Modals, 1990.

F. R. Palmer, Mood and Modality, 2001.
DOI : 10.1017/CBO9781139167178

R. Quirk, A Comprehensive Grammar of the English Language, 1985.

R. Salkie, R. Salkie, and P. Busuttil, On the notion 'Degree of Modality, Modality in English. Theory and Description. Mouton de Gruyter, pp.79-102, 2009.

A. Simon-vandenbergen, I think and its Dutch equivalents in parliamentary debates, Corpora and Cross-linguistics Research. Rodopi, pp.297-317, 1998.

N. Smith, Changes in the modals and semi-modals of strong obligation and epistemic necessity in recent British English, Modality in Contemporary English, pp.241-266, 2003.
DOI : 10.1515/9783110895339.241

M. Stubbs, 'A Matter of Prolonged Field Work': Notes Towards a Modal Grammar of English1, Applied Linguistics, vol.7, issue.1, pp.1-25, 1986.
DOI : 10.1093/applin/7.1.1

E. Sweetser, From Etymology to Pragmatics: Metaphorical and Cultural Aspects of Semantic Structure, 1990.
DOI : 10.1017/CBO9780511620904

E. Traugott, . Closs, B. Richard, and . Dasher, Regularity in Semantic Change, 2002.
DOI : 10.1017/CBO9780511486500

W. Van-belle, Modale en Performatieve Werkwoorden, pp.264-288, 1973.

A. Verhulst, A Corpus-based Analysis of Root Necessity Meanings Expressed by 'Should', 'Ought to' and 'Be Supposed to' in Late 20th, 2012.

J. Verstraete, Subjective and objective modality: interpersonal and ideational functions in the English modal auxiliary system, Journal of Pragmatics, vol.33, issue.10, pp.1505-1528, 2001.
DOI : 10.1016/S0378-2166(01)00029-7

P. Westney, Modals and Periphrastics in English, 1995.
DOI : 10.1515/9783110958904