code: func (g *Cloud) ToInstanceReferences(zone string, instanceNames []string) (refs []*compute.InstanceReference) {
  	for _, ins := range instanceNames {
  		instanceLink := makeHostURL(g.service.BasePath, g.projectID, zone, ins)
  		refs = append(refs, &compute.InstanceReference{Instance: instanceLink})
  	}
  	return refs
  }
docs: // ToInstanceReferences returns instance references by links