Notes. bundances with respect to total hydrogen nuclei. † To date, the cis conformer of HCOOH has only been detected towards the Orion Bar PDR (Cuadrado et al. 2016), therefore, we only provide the abundances of the trans conformer. ⁽¹⁾ This work. Abundances calculated assuming uniform beam filling. References: ^(a)Cuadrado et al. (2016). ⁽²⁾ Low-UV field Horsehead PDR (χ ≈ 60; N_H = 3.8 × 10²² cm^-2) and ⁽³⁾ condensation shielded from the UV field (dense core, N_H = 6.4 × 10²² cm^-2) behind the Horsehead PDR edge. Ref.: ^(b)Gerin et al. (2009), ^(c)Guzmán et al. (2011), ^(d)Guzmán et al. (2014), ^(e)Gratier et al. (2013), ^(f)Guzmán et al. (2013). ⁽⁴⁾ Orion KL Hot Core (HC); and ⁽⁵⁾ Orion KL Compact Ridge (CR). ⁽⁶⁾ Abundances calculated for the Extended Ridge. Ref.: ^(g)Blake et al. (1987), ^(h)Crockett et al. (2014), ⁽ⁱ⁾ B. Tercero, priv. comm.. ⁽⁷⁾ Peak B1 in the blue lobe of the L1157. Ref.: ^(k)Mendoza et al. (2014), ^(l)Bachiller & Pérez Gutiérrez (1997), ^(m)Codella et al. (2015). ⁽⁸⁾ Low-mass protostar (hot corino) IRAS 16293-2422. The abundances are computed for a N(H₂) = 2 × 10²³ cm^-2. Abundances averaged over a ~20′′ beam (van Dishoeck et al. 1995). ⁽⁹⁾ Quiescent dark core Barnard 1-b (B1-b), N(H₂) = 1.3 × 10²³ cm^-2 (see e.g. Hirano et al. 1999; Lis et al. 2002). Ref.: ⁽ⁿ⁾Cernicharo et al. (2012), ^(p)Marcelino et al. (2009),^(q)Marcelino et al. (2005), ^(r) N. Marcelino, priv. comm., ^(s) see also Öberg et al. (2010).