diff --git a/index.js b/index.js
index 7b9ca4ac..3e6965d9 100644
--- a/index.js
+++ b/index.js
@@ -198,6 +198,7 @@ const createClient = (profile, userAgent, opt = {}) => {
 				getIV: false, // todo: walk & bike as alternatives?
 				getPolyline: !!opt.polylines
 				// todo: `getConGroups: false` what is this?
+				// todo: what is getEco, fwrd?
 			}
 			if (profile.journeysNumF && opt.results !== null) query.numF = opt.results
 			if (profile.journeysOutFrwd) query.outFrwd = outFrwd
diff --git a/lib/request.js b/lib/request.js
index 022d3d69..40b0f611 100644
--- a/lib/request.js
+++ b/lib/request.js
@@ -35,7 +35,9 @@ const request = (ctx, userAgent, reqData) => {
 	const {profile, opt} = ctx
 
 	const body = profile.transformReqBody(ctx, {
-		lang: opt.language || 'en', // todo: is it `eng` actually?
+		// todo: is it `eng` actually?
+		// RSAG has `deu` instead of `de`
+		lang: opt.language || 'en',
 		svcReqL: [reqData]
 	})
 	if (DEBUG) console.error(JSON.stringify(body))
diff --git a/p/bvg/index.js b/p/bvg/index.js
index a37f5463..5b8b278f 100644
--- a/p/bvg/index.js
+++ b/p/bvg/index.js
@@ -23,6 +23,7 @@ const transformReqBody = (ctx, body) => {
 	return body
 }
 
+// todo: https://m.tagesspiegel.de/berlin/fahrerlebnis-wie-im-regionalexpress-so-faehrt-es-sich-in-der-neuen-express-s-bahn/25338674.html
 const parseLineWithMoreDetails = ({parsed}, p) => {
 	parsed.name = p.name.replace(/^(bus|tram)\s+/i, '')
 	const details = parseLineName(parsed.name)
diff --git a/p/db/loyalty-cards.js b/p/db/loyalty-cards.js
index dfb583e9..a4bdd719 100644
--- a/p/db/loyalty-cards.js
+++ b/p/db/loyalty-cards.js
@@ -1,5 +1,6 @@
 'use strict'
 
+// todo: generate from https://reiseauskunft.bahn.de/addons/fachkonfig-utf8.cfg ?
 const c = {
 	NONE: Symbol('no loyaly card'),
 	BAHNCARD: Symbol('Bahncard'),
diff --git a/p/vbb/index.js b/p/vbb/index.js
index 20c38f6d..5ce8c9c6 100644
--- a/p/vbb/index.js
+++ b/p/vbb/index.js
@@ -24,6 +24,7 @@ const transformReqBody = (ctx, body) => {
 	return body
 }
 
+// todo: https://m.tagesspiegel.de/berlin/fahrerlebnis-wie-im-regionalexpress-so-faehrt-es-sich-in-der-neuen-express-s-bahn/25338674.html
 const parseLineWithMoreDetails = ({parsed}, p) => {
 	parsed.name = p.name.replace(/^(bus|tram)\s+/i, '')
 	const details = parseLineName(parsed.name)
diff --git a/parse/arrival-or-departure.js b/parse/arrival-or-departure.js
index 90b4b3ec..43b599bd 100644
--- a/parse/arrival-or-departure.js
+++ b/parse/arrival-or-departure.js
@@ -7,6 +7,7 @@ const DEPARTURE = 'd'
 
 // todo: what is d.jny.dirFlg?
 // todo: d.stbStop.dProgType/d.stbStop.aProgType
+// todo: d.stbStop.dProdX/aProdX can be different than d.prodX
 
 const createParseArrOrDep = (prefix) => {
 	if (prefix !== ARRIVAL && prefix !== DEPARTURE) throw new Error('invalid prefix')
diff --git a/parse/hint.js b/parse/hint.js
index 14cdbe46..0288d5e5 100644
--- a/parse/hint.js
+++ b/parse/hint.js
@@ -23,6 +23,7 @@ const linkTypesByCode = Object.assign(Object.create(null), {
 // 	"RES_JNY_DTL" // only shown in journey detail
 // ]
 // todo: https://github.com/public-transport/hafas-client/issues/5
+// todo: expose h.type somehow
 const parseHint = (ctx, h) => {
 	// todo: C
 
diff --git a/parse/location.js b/parse/location.js
index f61f2713..232ccb0d 100644
--- a/parse/location.js
+++ b/parse/location.js
@@ -8,7 +8,10 @@ const ADDRESS = 'A'
 
 const leadingZeros = /^0+/
 
-// todo: what is s.rRefL?
+// todo: what is l.wt? is it "weight"?
+// 	- `6733` for 8013074 with p/vmt
+// 	- `3933` for 8012092 with p/vmt
+// 	- `2062` for 8010168 with p/vmt
 const parseLocation = (ctx, l) => {
 	const {profile, opt} = ctx
 
diff --git a/test/e2e/hvv.js b/test/e2e/hvv.js
index c3c9840a..6dfa13be 100644
--- a/test/e2e/hvv.js
+++ b/test/e2e/hvv.js
@@ -18,8 +18,6 @@ const testDepartures = require('./lib/departures')
 const testDeparturesInDirection = require('./lib/departures-in-direction')
 const testArrivals = require('./lib/arrivals')
 
-const isObj = o => o !== null && 'object' === typeof o && !Array.isArray(o)
-
 const when = createWhen('Europe/Berlin', 'de-DE')
 
 const cfg = {