Another issue that has been identified is that of limited co-operation between state authorities and NGOs within the country of origin.370 In a number of countries, national referral mechanisms have been established to formalize co-operation among government agencies and non-governmental organizations.371 However, it should be noted that the referral models in different countries vary widely, as do the scope and extent of their implementation.372 In most countries with national referral mechanisms, civil society plays a key role in the national co-ordination of anti-trafficking responses, including return.373 In some countries, formal co-operation agreements have been concluded between NGOs and state authorities. These co-operation agreements sometimes specify the roles and responsibilities of police and counselling centres for trafficked persons, including on referral, information sharing and the conduct of pre-return risk assessments.374 Problems with co-operation can prevent victims from accessing the full range of assistance and services available, and can limit them to the assistance provided by particular agencies and their partners.375 Such problems may also compromise victim safety, in particular if a lack of co-operation affects pre-return risk assessments or the provision of protection. For example, in some countries it has been reported that difficulties in co-operation between law enforcement and those providing counselling to returning victims have led to inadequate risk assessments.376 In addition to national referral mechanisms, some states have also formalized co-operation between state agencies and civil society, through legislation or by-laws, or through policy documents or protocols. The existence of national anti-trafficking programmes specifying the roles of key actors has contributed to increased co-ordination in trafficking responses.377 Concerns have been raised about the existence, quality and duration of monitoring carried out following victims’ return and during their period of reintegration. Few countries of destination, or indeed of origin, maintain contact with victims after return.378 Even countries of origin that specifically provide for reintegration assistance report a lack of effective post-return monitoring in most cases. 370 UNODC, Human Trafficking in the Baltic Sea Region, op. cit., note 37, p. 39. 371 OSCE/ODIHR, National Referral Mechanisms – Joining Efforts to Protect the Rights of Trafficked Persons: A Practical Handbook (Warsaw: ODIHR, 2004). 372 Surtees, Listening to Victims, op. cit., note 77, p. 47. 373  OSCE Office of the Special Representative and Co-ordinator for Combating Trafficking in Human Beings, Efforts to Combat Trafficking in Human Beings in the OSCE Area: Co-ordination and Reporting Mechanisms (Vienna: OSCE, 2008), p. 11. 374  See, for example Kooperationskonzept für die Zusammenarbeit von Fachberatungsstellen und Polizei für den Schutz von Opferzeugen/innen von Menschenhandel zum Zweck der sexuellen Ausbeutung, Bundesministerium für Familie, Senioren, Frauen und Jugend, 2007 (in German only). 375 Surtees, Listening to Victims, op. cit., note 77, p. 44. 376 UNODC, Human Trafficking in the Baltic Sea Region, op. cit., note 37, p. 43. 377  Hancilova and Massey, Legislation and the Situation Concerning Trafficking in Human Beings, op. cit., note 80, p. 93. 378  European Migration Network (EMN), Programmes and Strategies, p. 79. 92 Part 2: Explanatory Report to the Principles