user-1: Lineage is important to teaching by gurus and the succession of teaching because it helps ensure that the teaching is complete and intact, and that the teachers are sincere. One must be granted permission to teach by one's Guru, which means that by using Induction, we can see that all lineages must go back to the Buddha himself.
But I wonder, in the modern world, if this has not become irrelevant? Any person can find the teachings now, in various translations, and so the issue falls on that person to determine what they feel is legitimate. Modern people are unlikely to become monks, and I have never seen any definitive statement that laypeople never can achieve enlightenment (rather the opposite). One need not join a community, follow a guru or even know another person with the same 'theories' to practice and make progress.
So, is lineage still important? Can we not fix down a translation of the books, make them public, offer opportunities for retreats or guidance and just allow people to choose and go forward for themselves? There is no particular lineage in science, even if some persons are well-regarded and often referred to. Anyone with access to a library could become a Physicist, regardless what schools they go to, or whom the teachers studied under. The knowledge is the guru, not a person. In fact, the Buddha said, "Be ye lamps unto yourselves." Is this not what he meant?

user43: From student's perspective, studying explicitly under a lineage is supposed to give you a sense of reliable traditional foundation empowering your practice. This is similar to the feeling you get when you go to an Ivy League university, you have a very strong sense that the very walls of the institution are permeated with science, and this acts as an inspiration and gives you energy to strive forward.
From teacher's perspective, the main benefit that affiliation with lineage gives you is what I call the "abstract blessings". Meaning, as an authorized lineage holder you would feel entitlement, support, and abstract power of lineage - as something that gives you strength and increases your faith in the teaching and confidence in yourself, esp. in case of adverse circumstances.
This comes with its price of course. Effectively, you are relying on an abstract entity (the so-called spirit of the lineage) which is a relationship of co-dependency. If you think about it, in a mild form it's the same type of contract you get into with a deity in traditional monotheistic or pagan religion. You serve and support the entity and in return the entity gives you it's power and support.
I personally have a philosophical problem with these kinds of arrangements. Call me selfish, but for me freedom from dependency is more important than the support I'd get from an institution, however tempting that may be. Plus, in my opinion, if your Awakening is worth its salt, you should be absolutely able to function as teacher without any official authorization.
Of course your question was more about authoritative/reliable sources of information on Dharma, rather than these more complicated matters - and I will let other people handle those, but here I wanted to share my thoughts on the above, hoping it will be useful for someone downstream.

user-1: I think most people miss one of the greatest benefits of studying under a particular lineage.  Namely following a lineage very much narrows the scope of your practice.  Lineages aren't so much a heritage as they are a finely honed program of Buddhist study.  Dharma gates are without measure.  Most lineages have their own internal progression and have developed their own spiritual grammar that help their adherents quickly navigate through those dharma gates that offer the most expedient path to the most panoramic views.  Lineages can also require that a student develop a sense of trust in their teachings, lineage holders, and their teaching methodologies.  Developing faith and commitment of this sort is of paramount importance if one is to having any success on the Buddhist path.  
These days, it is all too easy to fall into syncretism or dharma cherry picking.  Modern students are very much prone to go from teacher to teacher, book to book, and retreat center to retreat center.  They keep what they like and - and this is the great danger - avoid the things they don't or find challenging.  Rather than question a teaching or look for an easier answer elsewhere, our trust in our own lineage demands that we investigate our resistance and overcome our self-made obstacles.        

user8157: Lineage is for those who do not take refuge in the Buddha & Dhamma of the Pali suttas. 

user-1: It since ever merely unlikely that many find lineage and liberation, but not impossible, having the "luck" coming in contact.
asked/suggested: In fact, the Buddha said, "Be ye lamps unto yourselves." Is this not what he meant?
The Buddha said that to those having already changed to the "lineage" of the Noble Ones, not at all and never to wordilings.
In fact (the act of) the Buddha did not uphold something more importand outwardly as the teacher/admirable friend and pointed strongly on the ancestorship of the lineage:

It is in dependence on me as an admirable friend that beings subject to birth have gained release from birth, that beings subject to aging have gained release from aging, that beings subject to death have gained release from death, that beings subject to sorrow, lamentation, pain, distress, & despair have gained release from sorrow, lamentation, pain, distress, & despair. It is through this line of reasoning that one may know how having admirable friendship, admirable companionship, admirable camaraderie is actually the whole of the holy life."
— SN 45.2

This heritage, to keep it alive, he gave to the Sangha of his disciples, his monks.
Such as Gurus and people outside of the Sangha, especially under lay people, even to draw such as "lineage", is neither given by the teacher nor in any way able to transmit the good Dhamma by nature.
Also that there is such as permission invented in this lineage to teach, is a trader invented mythos, selling pride and identification to merely fools.
Such is pure business and livelihood on Dhamma of which the Buddha put a lot of means into to avoid it.
How ever, "lineage" or better "ancestorship" o the Noble Ones is not gained by birth or outwardly signs and affiliation but by the first stage of awakening, by gaining gotrabhū-ñāṇaṃ
From this moment on, and only from here, one can regard him/herself being talked to when spoken: "make you self an island with the Dhamma (you already have really gained)"

the beginning of lineage...And while this explanation was being given, there arose to Ven. Kondañña the dustless, stainless Dhamma eye—...
...Then ..., having seen the Dhamma, having attained the Dhamma, having known the Dhamma, having fathomed the Dhamma, having crossed over and beyond uncertainty, having no more perplexity, having gained fearlessness, independence of others with regard to the Teacher’s message, ...

While it's not the most bad idea to turn away from Dhamma-dealers and "pyramid-trade" systems, is not smart to turn away from the most needed refuge to stay and have contact with the others, the Sangha.
As maybe observed, there is no such as a formal and regulated disciple-student relation between the members and the Sangha given, as such would neither work, or as we might have faced, leads to very problematic situations. So the relation, aside of natural laws, between lay people and Monks is a total voluntery one, purely based on goodness and generosity, without any formal personal duties.
As it is thought, this field of merits, can possible stay an independent source of teachers of the good Dhamma, others then later developments, copies and thieves for livelyhoods.
On the other hand, by person has not that much doubt that the Juwels, beginning with the Savaka Sangha, will fast disappear in the modern world and not even imagenable for the modern people. That's nature of modern (followed after by many).
Try to be wise and uproot the cause of incapacity of devotion and being capable to be tamed, you ego-tripps.
There would be just immense suffering able to teach you but possible no more refuge avaliable.
Good advices how to find oes good tracher are found in the essay: The Power of Judgment.
More on the topic student teacher relation might be found by one here: [Q&A] Proper way to ask a teacher to become their student
[Note: This is a gift of Dhamma and not meant for commercial purpose or other low wordily gains by means of trade and exchange.]

-1: <p>Lineage is important to teaching by gurus and the succession of teaching because it helps ensure that the teaching is complete and intact, and that the teachers are sincere. One must be granted permission to teach by one's Guru, which means that by using Induction, we can see that all lineages must go back to the Buddha himself.</p>

<p>But I wonder, in the modern world, if this has not become irrelevant? Any person can find the teachings now, in various translations, and so the issue falls on that person to determine what they feel is legitimate. Modern people are unlikely to become monks, and I have never seen any definitive statement that laypeople never can achieve enlightenment (rather the opposite). One need not join a community, follow a guru or even know another person with the same 'theories' to practice and make progress.</p>

<p>So, is lineage still important? Can we not fix down a translation of the books, make them public, offer opportunities for retreats or guidance and just allow people to choose and go forward for themselves? There is no particular lineage in science, even if some persons are well-regarded and often referred to. Anyone with access to a library could become a Physicist, regardless what schools they go to, or whom the teachers studied under. The knowledge is the guru, not a person. In fact, the Buddha said, "Be ye lamps unto yourselves." Is this not what he meant?</p>
 43: <p>From student's perspective, studying explicitly under a lineage is supposed to give you a sense of reliable traditional foundation empowering your practice. This is similar to the feeling you get when you go to an Ivy League university, you have a very strong sense that the very walls of the institution are permeated with science, and this acts as an inspiration and gives you energy to strive forward.</p>

<p>From teacher's perspective, the main benefit that affiliation with lineage gives you is what I call the "abstract blessings". Meaning, as an authorized lineage holder you would feel entitlement, support, and abstract power of lineage - as something that gives you strength and increases your faith in the teaching and confidence in yourself, esp. in case of adverse circumstances.</p>

<p>This comes with its price of course. Effectively, you are relying on an abstract entity (the so-called spirit of the lineage) which is a relationship of co-dependency. If you think about it, in a mild form it's the same type of contract you get into with a deity in traditional monotheistic or pagan religion. You serve and support the entity and in return the entity gives you it's power and support.</p>

<p>I personally have a philosophical problem with these kinds of arrangements. Call me selfish, but for me freedom from dependency is more important than the support I'd get from an institution, however tempting that may be. Plus, in my opinion, if your Awakening is worth its salt, you should be absolutely able to function as teacher without any official authorization.</p>

<p>Of course your question was more about authoritative/reliable sources of information on Dharma, rather than these more complicated matters - and I will let other people handle those, but here I wanted to share my thoughts on the above, hoping it will be useful for someone downstream.</p>
 -1: <p>I think most people miss one of the greatest benefits of studying under a particular lineage.  Namely following a lineage very much narrows the scope of your practice.  Lineages aren't so much a heritage as they are a finely honed program of Buddhist study.  Dharma gates are without measure.  Most lineages have their own internal progression and have developed their own spiritual grammar that help their adherents quickly navigate through those dharma gates that offer the most expedient path to the most panoramic views.  Lineages can also require that a student develop a sense of trust in their teachings, lineage holders, and their teaching methodologies.  Developing faith and commitment of this sort is of paramount importance if one is to having any success on the Buddhist path.  </p>

<p>These days, it is all too easy to fall into syncretism or dharma cherry picking.  Modern students are very much prone to go from teacher to teacher, book to book, and retreat center to retreat center.  They keep what they like and - and this is the great danger - avoid the things they don't or find challenging.  Rather than question a teaching or look for an easier answer elsewhere, our trust in our own lineage demands that we investigate our resistance and overcome our self-made obstacles.        </p>
 8157: <p>Lineage is for those who do not take refuge in the Buddha &amp; Dhamma of the Pali suttas. </p>
 -1: <p>It since ever merely unlikely that many find lineage and liberation, but not impossible, having the &quot;luck&quot; coming in contact.</p>
<p><strong>asked/suggested:</strong> <code>In fact, the Buddha said, &quot;Be ye lamps unto yourselves.&quot; Is this not what he meant?</code></p>
<p>The Buddha said that to those having already changed to the &quot;lineage&quot; of the Noble Ones, not at all and never to wordilings.</p>
<p>In fact (the act of) the Buddha did not uphold something more <a href="http://zugangzureinsicht.org/html/tipitaka/kn/iti/iti.1.001-027.than_en.html#iti-017" rel="nofollow noreferrer">importand outwardly</a> as the teacher/<a href="http://zugangzureinsicht.org/html/ptf/dhamma/sacca/sacca4/samma-ditthi/kalyanamittata_en.html" rel="nofollow noreferrer">admirable friend</a> and pointed strongly on the ancestorship of the lineage:</p>
<blockquote>
<p>It is in dependence on me as an admirable friend that beings subject to birth have gained release from birth, that beings subject to aging have gained release from aging, that beings subject to death have gained release from death, that beings subject to sorrow, lamentation, pain, distress, &amp; despair have gained release from sorrow, lamentation, pain, distress, &amp; despair. It is through this line of reasoning that one may know how having admirable friendship, admirable companionship, admirable camaraderie is actually the whole of the holy life.&quot;</p>
<p>— SN 45.2</p>
</blockquote>
<p>This heritage, to keep it alive, he gave to the Sangha of his disciples, his monks.</p>
<p>Such as Gurus and people outside of the Sangha, especially under lay people, even to draw such as &quot;lineage&quot;, is neither given by the teacher nor in any way able to transmit the good Dhamma by nature.</p>
<p>Also that there is such as permission invented in this lineage to teach, is a trader invented mythos, selling pride and identification to merely fools.</p>
<p>Such is pure business and livelihood on Dhamma of which the Buddha put a lot of means into to avoid it.</p>
<p>How ever, &quot;lineage&quot; or better &quot;ancestorship&quot; o the Noble Ones is not gained by birth or outwardly signs and affiliation but by the first stage of awakening, by gaining <em><a href="http://zugangzureinsicht.org/html/lib/authors/nanadassana/wisdom_en.html#fn-22" rel="nofollow noreferrer">gotrabhū-ñāṇaṃ</a></em></p>
<p>From this moment on, and only from here, one can regard him/herself being talked to when spoken: &quot;make you self an island with the Dhamma (you already have really gained)&quot;</p>
<blockquote>
<p><em><a href="http://sangham.net/index.php/topic,8043.msg13286.html#msg13286" rel="nofollow noreferrer">the beginning of lineage</a></em>...And while this explanation was being given, there arose to Ven. Kondañña the dustless, stainless Dhamma eye—...</p>
<p>...Then ..., having seen the Dhamma, having attained the Dhamma, having known the Dhamma, having fathomed the Dhamma, having crossed over and beyond uncertainty, having no more perplexity, having gained fearlessness, independence of others with regard to the Teacher’s message, ...</p>
</blockquote>
<p>While it's not the most bad idea to turn away from Dhamma-dealers and &quot;pyramid-trade&quot; systems, is not smart to turn away from the most needed refuge to stay and have contact with the others, the Sangha.</p>
<p>As maybe observed, there is no such as a formal and regulated disciple-student relation between the members and the Sangha given, as such would neither work, or as we might have faced, leads to very problematic situations. So the relation, aside of natural laws, between lay people and Monks is a total voluntery one, purely based on goodness and generosity, without any formal personal duties.</p>
<p>As it is thought, this field of merits, can possible stay an independent source of teachers of the good Dhamma, others then later developments, copies and thieves for livelyhoods.</p>
<p>On the other hand, by person has not that much doubt that the Juwels, beginning with the Savaka Sangha, will fast disappear in the modern world and not even imagenable for the modern people. That's nature of modern (followed after by many).</p>
<p>Try to be wise and uproot the cause of incapacity of devotion and being capable to be tamed, you ego-tripps.</p>
<p>There would be just immense suffering able to teach you but possible no more refuge avaliable.</p>
<p>Good advices how to find oes good tracher are found in the essay: <a href="http://zugangzureinsicht.org/html/lib/authors/thanissaro/power_of_judgment_en.html" rel="nofollow noreferrer">The Power of Judgment</a>.</p>
<p>More on the topic student teacher relation might be found by one here: <a href="http://sangham.net/index.php/topic,8135.msg12395.html#msg12395" rel="nofollow noreferrer">[Q&amp;A] Proper way to ask a teacher to become their student</a></p>
<p><em>[Note: This is a gift of Dhamma and not meant for commercial purpose or other low wordily gains by means of trade and exchange.]</em></p>
